8.1. datetime — Tipos básicos de data e hora

Código Fonte: Lib/datetime.py

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O módulo datetime fornece classes para manipular datas e tempo de forma simples ou complexas. Apesar de cálculos aritméticos com data e tempo serem suportados, o foco da implementação está na extração eficiente de atributo para formatar resultados e manipulação. Para funcionalidades relacionadas, veja também os módulos time e calendar.

There are two kinds of date and time objects: “naive” and “aware”.

An aware object has sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, to locate itself relative to other aware objects. An aware object is used to represent a specific moment in time that is not open to interpretation 1.

A naive object does not contain enough information to unambiguously locate itself relative to other date/time objects. Whether a naive object represents Coordinated Universal Time (UTC), local time, or time in some other timezone is purely up to the program, just like it is up to the program whether a particular number represents metres, miles, or mass. Naive objects are easy to understand and to work with, at the cost of ignoring some aspects of reality.

For applications requiring aware objects, datetime and time objects have an optional time zone information attribute, tzinfo, that can be set to an instance of a subclass of the abstract tzinfo class. These tzinfo objects capture information about the offset from UTC time, the time zone name, and whether Daylight Saving Time is in effect. Note that only one concrete tzinfo class, the timezone class, is supplied by the datetime module. The timezone class can represent simple timezones with fixed offset from UTC, such as UTC itself or North American EST and EDT timezones. Supporting timezones at deeper levels of detail is up to the application. The rules for time adjustment across the world are more political than rational, change frequently, and there is no standard suitable for every application aside from UTC.

O módulo datetime exporta as seguintes constantes:

datetime.MINYEAR

O menor número de ano permitido no objeto :classe`date` ou :classe`.datetime` . :const`MINYEAR` é 1.

datetime.MAXYEAR

O maior número de ano permitido no objeto :classe`date` ou :classe`.datetime` . :const`MAXYER` é 9999.

Ver também

Módulo calendar

Funções gerais relacionadas ao calendário.

Módulo time

Acesso de hora e conversões.

8.1.1. Tipos disponíveis

class datetime.date

Uma data ingênua idealizada, assumindo que o atual calendário Gregoriano sempre foi, e sempre estará em vigor. Atributos: year, month, e day.

class datetime.time

An idealized time, independent of any particular day, assuming that every day has exactly 24*60*60 seconds (there is no notion of “leap seconds” here). Attributes: hour, minute, second, microsecond, and tzinfo.

class datetime.datetime

Uma combinação de uma data e uma hora. Atributos: ano, mês, dia, hora, minuto, segundo, microsegundo, e tzinfo.

class datetime.timedelta

Uma duração que expressa a diferença entre duas instâncias date, time ou datetime para resolução de microssegundos.

class datetime.tzinfo

An abstract base class for time zone information objects. These are used by the datetime and time classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time).

class datetime.timezone

Uma classe que implementa a classe base abstrata :classe:`tzinfo` como um deslocamento fixo do UTC.

Novo na versão 3.2.

Objetos desses tipos são imutáveis.

Objetos do tipo: classe`date` são sempre ingênuos.

An object of type time or datetime may be naive or aware. A datetime object d is aware if d.tzinfo is not None and d.tzinfo.utcoffset(d) does not return None. If d.tzinfo is None, or if d.tzinfo is not None but d.tzinfo.utcoffset(d) returns None, d is naive. A time object t is aware if t.tzinfo is not None and t.tzinfo.utcoffset(None) does not return None. Otherwise, t is naive.

The distinction between naive and aware doesn’t apply to timedelta objects.

Relacionamentos de subclasses:

object
    timedelta
    tzinfo
        timezone
    time
    date
        datetime

8.1.2. timedelta Objetos

O objeto timedelta representa uma duração, a diferença entre duas datas ou horas.

class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)

All arguments are optional and default to 0. Arguments may be integers or floats, and may be positive or negative.

Only days, seconds and microseconds are stored internally. Arguments are converted to those units:

• Um milissegundo é convertido em 1000 microssegundos.

• Um minuto é convertido em 60 segundos.

• Uma hora é convertida em 3600 segundos.

• Uma semana é convertida para 7 dias.

e dias, segundos e microssegundos são normalizados para que a representação seja única, com

• 0 <= microsegundos < 1000000

• 0 <= seconds < 3600*24 (o número de segundos em um dia)

• -999999999 <= dias <= 999999999

If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond using round-half-to-even tiebreaker. If no argument is a float, the conversion and normalization processes are exact (no information is lost).

Se o valor normalizado de dias estiver fora do intervalo indicado, OverflowError é gerado.

Note that normalization of negative values may be surprising at first. For example,

>>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)

Class attributes are:

timedelta.min

O mais negativo objeto timedelta, timedelta(-999999999).

timedelta.max

O mais positivo objeto timedelta, timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999).

timedelta.resolution

A menor diferença possível entre objetos não iguais timedelta, timedelta(microseconds=1).

Observe que, devido à normalização, timedelta.max > -timedelta.min. -timedelta.max não é representável como um objeto timedelta.

Atributos de instância (somente leitura):

Atributo	Valor
days	Entre -999999999 e 999999999 inclusive
seconds	Entre 0 e 86399 inclusive
microseconds	Entre 0 e 999999 inclusive

Operações suportadas:

Operação	Resultado
t1 = t2 + t3	Soma de t2 e t3. Depois t1-t2 == t3 e t1-t3 == t2 são verdadeiros. (1)
t1 = t2 - t3	Diferença de t2 e t3. Depois t1 == t2 - t3 e t2 == t1 + t3 são verdadeiros (1)(6)
t1 = t2 * i ou t1 = i * t2	Delta multiplicado por um número inteiro. Depois t1 // i == t2 é verdadeiro, desde que i != 0.
	Em geral, t1 * i == t1 * (i-1) + t1 é verdadeiro. (1)
t1 = t2 * f or t1 = f * t2	Delta multiplicado por um float, ponto flutuante. O resultado é arredondado para o múltiplo mais próximo de timedelta.resolution usando a metade da metade para o par.
f = t2 / t3	Division (3) of t2 by t3. Returns a float object.
t1 = t2 / f or t1 = t2 / i	Delta dividido por um float ou um int. O resultado é arredondado para o múltiplo mais próximo de timedelta.resolution usando a metade da metade para o par.
t1 = t2 // i or t1 = t2 // t3	The floor is computed and the remainder (if any) is thrown away. In the second case, an integer is returned. (3)
t1 = t2 % t3	O restante é calculado como um objeto timedelta. (3)
q, r = divmod(t1, t2)	Calcula o quociente e o restante: q = t1 // t2 (3) e r = t1% t2. q é um número inteiro e r é um objeto timedelta.
+t1	Retorna um objeto timedelta com o mesmo valor. (2)
-t1	equivalente a timedelta(-t1.days, -t1.seconds, -t1.microseconds), e a t1* -1. (1)(4)
abs(t)	equivalente a + t quando t.days> = 0, e a - t quando t.days <0. (2)
str(t)	Retorna uma string no formato [D day[s], ][H]H:MM:SS[.UUUUUU], onde D é negativo para t negativo. (5)
repr(t)	Returns a string in the form datetime.timedelta(D[, S[, U]]), where D is negative for negative t. (5)

Notas:

1. This is exact, but may overflow.

2. This is exact, and cannot overflow.

3. A divisão por 0 gera ZeroDivisionError.

4. -timedelta.max não é representável como um objeto timedelta.

5. String representations of timedelta objects are normalized similarly to their internal representation. This leads to somewhat unusual results for negative timedeltas. For example:

   >>> timedelta(hours=-5)
   datetime.timedelta(-1, 68400)
   >>> print(_)
   -1 day, 19:00:00
   

6. A expressão t2 - t3 sempre será igual à expressão t2 + (-t3) exceto quando t3 for igual a timedelta.max; nesse caso, o primeiro produzirá um resultado enquanto o último transbordará.

In addition to the operations listed above timedelta objects support certain additions and subtractions with date and datetime objects (see below).

Alterado na versão 3.2: Floor division and true division of a timedelta object by another timedelta object are now supported, as are remainder operations and the divmod() function. True division and multiplication of a timedelta object by a float object are now supported.

Comparisons of timedelta objects are supported with the timedelta object representing the smaller duration considered to be the smaller timedelta. In order to stop mixed-type comparisons from falling back to the default comparison by object address, when a timedelta object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively.

timedelta objects are hashable (usable as dictionary keys), support efficient pickling, and in Boolean contexts, a timedelta object is considered to be true if and only if it isn’t equal to timedelta(0).

Métodos de instância:

timedelta.total_seconds()

Return the total number of seconds contained in the duration. Equivalent to td / timedelta(seconds=1).

Observe que, em intervalos de tempo muito grandes (mais de 270 anos na maioria das plataformas), esse método perde a precisão de microssegundos.

Novo na versão 3.2.

Example usage:

>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> another_year = timedelta(weeks=40, days=84, hours=23,
...                          minutes=50, seconds=600)  # adds up to 365 days
>>> year.total_seconds()
31536000.0
>>> year == another_year
True
>>> ten_years = 10 * year
>>> ten_years, ten_years.days // 365
(datetime.timedelta(3650), 10)
>>> nine_years = ten_years - year
>>> nine_years, nine_years.days // 365
(datetime.timedelta(3285), 9)
>>> three_years = nine_years // 3;
>>> three_years, three_years.days // 365
(datetime.timedelta(1095), 3)
>>> abs(three_years - ten_years) == 2 * three_years + year
True

8.1.3. date Objetos

A date object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions. January 1 of year 1 is called day number 1, January 2 of year 1 is called day number 2, and so on. This matches the definition of the “proleptic Gregorian” calendar in Dershowitz and Reingold’s book Calendrical Calculations, where it’s the base calendar for all computations. See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems.

class datetime.date(year, month, day)

All arguments are required. Arguments may be integers, in the following ranges:

• MINYEAR <= year <= MAXYEAR

• 1 <= month <= 12

• 1 <= day <= number of days in the given month and year

Se um argumento fora desses intervalos for fornecido, ValueError é levantado.

Outros construtores, todos os métodos de classe.

classmethod date.today()

Return the current local date. This is equivalent to date.fromtimestamp(time.time()).

classmethod date.fromtimestamp(timestamp)

Return the local date corresponding to the POSIX timestamp, such as is returned by time.time(). This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() function, and OSError on localtime() failure. It’s common for this to be restricted to years from 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp().

Alterado na versão 3.3: Levanta OverflowError ao invés de ValueError se o carimbo de data/hora estiver fora do intervalo de valores suportados pela plataforma C localtime() função. Levanta OSError ao invés de ValueError em falha de localtime() .

classmethod date.fromordinal(ordinal)

Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1 <= ordinal <= date.max.toordinal(). For any date d, date.fromordinal(d.toordinal()) == d.

Atributos de classe:

date.min

A data representável mais antiga, date(MINYEAR, 1, 1).

date.max

A data representável mais tardia, date(MAXYEAR, 12, 31).

date.resolution

A menor diferença possível entre objetos date não iguais, timedelta(days=1).

Atributos de instância (somente leitura):

date.year

Entre MINYEAR e MAXYEAR incluindo extremos.

date.month

Entre 1 e 12 incluindo extremos.

date.day

Entre 1 e o número de dias no mês especificado do ano especificado.

Operações suportadas:

Operação	Resultado
date2 = date1 + timedelta	date2 is timedelta.days days removed from date1. (1)
date2 = date1 - timedelta	Computa date2 de modo que date2 + timedelta == date1. (2)
timedelta = date1 - date2	(3)
date1 < date2	date1 é considerada menor que date2 quando date1 precede date2 no tempo. (4)

Notas:

1. date2 is moved forward in time if timedelta.days > 0, or backward if timedelta.days < 0. Afterward date2 - date1 == timedelta.days. timedelta.seconds and timedelta.microseconds are ignored. OverflowError is raised if date2.year would be smaller than MINYEAR or larger than MAXYEAR.

2. timedelta.seconds e timedelta.microseconds são ignoradas.

3. This is exact, and cannot overflow. timedelta.seconds and timedelta.microseconds are 0, and date2 + timedelta == date1 after.

4. In other words, date1 < date2 if and only if date1.toordinal() < date2.toordinal(). Date comparison raises TypeError if the other comparand isn’t also a date object. However, NotImplemented is returned instead if the other comparand has a timetuple() attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a date object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively.

Dates can be used as dictionary keys. In Boolean contexts, all date objects are considered to be true.

Métodos de instância:

date.replace(year=self.year, month=self.month, day=self.day)

Return a date with the same value, except for those parameters given new values by whichever keyword arguments are specified. For example, if d == date(2002, 12, 31), then d.replace(day=26) == date(2002, 12, 26).

date.timetuple()

Return a time.struct_time such as returned by time.localtime(). The hours, minutes and seconds are 0, and the DST flag is -1. d.timetuple() is equivalent to time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1)), where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st.

date.toordinal()

Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d, date.fromordinal(d.toordinal()) == d.

date.weekday()

Retorna o dia da semana como um inteiro, onde Segunda é 0 e Domingo é 6. Por exemplo, date(2002, 12, 4).weekday() == 2, uma Quarta-feira. Veja também isoweekday().

date.isoweekday()

Retorna o dia da semana como um inteiro, onde Segunda é 1 e Domingo é 7. Por exemplo, date(2002, 12, 4).isoweekday() == 3, uma Quarta-feira. Veja também weekday(), isocalendar().

date.isocalendar()

Return a 3-tuple, (ISO year, ISO week number, ISO weekday).

The ISO calendar is a widely used variant of the Gregorian calendar. See https://www.staff.science.uu.nl/~gent0113/calendar/isocalendar.htm for a good explanation.

The ISO year consists of 52 or 53 full weeks, and where a week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday. This is called week number 1, and the ISO year of that Thursday is the same as its Gregorian year.

For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004, so that date(2003, 12, 29).isocalendar() == (2004, 1, 1) and date(2004, 1, 4).isocalendar() == (2004, 1, 7).

date.isoformat()

Return a string representing the date in ISO 8601 format, ‘YYYY-MM-DD’. For example, date(2002, 12, 4).isoformat() == '2002-12-04'.

date.__str__()

Para um objeto date d, str(d) é equivalente a d.isoformat().

date.ctime()

Return a string representing the date, for example date(2002, 12, 4).ctime() == 'Wed Dec 4 00:00:00 2002'. d.ctime() is equivalent to time.ctime(time.mktime(d.timetuple())) on platforms where the native C ctime() function (which time.ctime() invokes, but which date.ctime() does not invoke) conforms to the C standard.

date.strftime(format)

Retorna uma string representando a data, controlado por uma string explícita de formatação. Códigos de formatação referenciando horas, minutos ou segundos irão ver valores 0. Para uma lista completa de diretivas de formatação, veja Comportamento de strftime() e strptime().

date.__format__(format)

O mesmo que date.strftime(). Isso torna possível especificar uma string de formatação para o objeto date em literais de string formatados e ao usar str.format(). Para uma lista completa de diretivas de formatação, veja Comportamento de strftime() e strptime().

Exemplo de contagem de dias para um evento:

>>> import time
>>> from datetime import date
>>> today = date.today()
>>> today
datetime.date(2007, 12, 5)
>>> today == date.fromtimestamp(time.time())
True
>>> my_birthday = date(today.year, 6, 24)
>>> if my_birthday < today:
...     my_birthday = my_birthday.replace(year=today.year + 1)
>>> my_birthday
datetime.date(2008, 6, 24)
>>> time_to_birthday = abs(my_birthday - today)
>>> time_to_birthday.days
202

Example of working with date:

>>> from datetime import date
>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001
>>> d
datetime.date(2002, 3, 11)
>>> t = d.timetuple()
>>> for i in t:     
...     print(i)
2002                # year
3                   # month
11                  # day
0
0
0
0                   # weekday (0 = Monday)
70                  # 70th day in the year
-1
>>> ic = d.isocalendar()
>>> for i in ic:    
...     print(i)
2002                # ISO year
11                  # ISO week number
1                   # ISO day number ( 1 = Monday )
>>> d.isoformat()
'2002-03-11'
>>> d.strftime("%d/%m/%y")
'11/03/02'
>>> d.strftime("%A %d. %B %Y")
'Monday 11. March 2002'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")
'The day is 11, the month is March.'

8.1.4. Objetos datetime

A datetime object is a single object containing all the information from a date object and a time object. Like a date object, datetime assumes the current Gregorian calendar extended in both directions; like a time object, datetime assumes there are exactly 3600*24 seconds in every day.

Construtor:

class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

The year, month and day arguments are required. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments may be integers, in the following ranges:

• MINYEAR <= year <= MAXYEAR,

• 1 <= month <= 12,

• ``1 <= day <= número de dias no mês e ano fornecidos`,

• 0 <= hour < 24,

• 0 <= minute < 60,

• 0 <= second < 60,

• 0 <= microsecond < 1000000,

• fold in [0, 1].

Se um argumento fora desses intervalos for fornecido, ValueError é levantado.

Novo na versão 3.6: Adicionado o argumento fold.

Outros construtores, todos os métodos de classe.

classmethod datetime.today()

Return the current local datetime, with tzinfo None. This is equivalent to datetime.fromtimestamp(time.time()). See also now(), fromtimestamp().

classmethod datetime.now(tz=None)

Return the current local date and time. If optional argument tz is None or not specified, this is like today(), but, if possible, supplies more precision than can be gotten from going through a time.time() timestamp (for example, this may be possible on platforms supplying the C gettimeofday() function).

If tz is not None, it must be an instance of a tzinfo subclass, and the current date and time are converted to tz’s time zone. In this case the result is equivalent to tz.fromutc(datetime.utcnow().replace(tzinfo=tz)). See also today(), utcnow().

classmethod datetime.utcnow()

Return the current UTC date and time, with tzinfo None. This is like now(), but returns the current UTC date and time, as a naive datetime object. An aware current UTC datetime can be obtained by calling datetime.now(timezone.utc). See also now().

classmethod datetime.fromtimestamp(timestamp, tz=None)

Retorna a data e hora local correspondente ao timestamp POSIX, como é retornado por time.time(). Se o argumento opcional tz é None ou não especificado, o timestamp é convertido para a data e hora local da plataforma, e o objeto datetime retornado é ingênuo.

If tz is not None, it must be an instance of a tzinfo subclass, and the timestamp is converted to tz’s time zone. In this case the result is equivalent to tz.fromutc(datetime.utcfromtimestamp(timestamp).replace(tzinfo=tz)).

fromtimestamp() may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions, and OSError on localtime() or gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp(), and then it’s possible to have two timestamps differing by a second that yield identical datetime objects. See also utcfromtimestamp().

Alterado na versão 3.3: Levanta um OverflowError ao invés de ValueError se o timestamp estiver fora do intervalo dos valores suportados pelas funções C localtime() ou gmtime() da plataforma. Levanta OSError ao invés de ValueError em falhas de localtime() ou gmtime().

Alterado na versão 3.6: fromtimestamp() pode retornar instâncias com fold igual a 1.

classmethod datetime.utcfromtimestamp(timestamp)

Return the UTC datetime corresponding to the POSIX timestamp, with tzinfo None. This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C gmtime() function, and OSError on gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038.

Para conseguir um objeto datetime consciente, chame fromtiemstamp():

datetime.fromtimestamp(timestamp, timezone.utc)

Nas plataformas compatíveis com POSIX, é equivalente à seguinte expressão:

datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)

com a exceção de que a última fórmula sempre dá suporte ao intervalo completo de anos: entre MINYEAR e MAXYEAR inclusive.

Alterado na versão 3.3: Levanta OverflowError ao invés de ValueError se o timestamp estiver fora do intervalo de valores suportados pela função C gmtime() da plataforma. Levanta OSError ao invés de ValueError em caso de falha gmtime().

classmethod datetime.fromordinal(ordinal)

Return the datetime corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1 <= ordinal <= datetime.max.toordinal(). The hour, minute, second and microsecond of the result are all 0, and tzinfo is None.

classmethod datetime.combine(date, time, tzinfo=self.tzinfo)

Return a new datetime object whose date components are equal to the given date object’s, and whose time components are equal to the given time object’s. If the tzinfo argument is provided, its value is used to set the tzinfo attribute of the result, otherwise the tzinfo attribute of the time argument is used.

For any datetime object d, d == datetime.combine(d.date(), d.time(), d.tzinfo). If date is a datetime object, its time components and tzinfo attributes are ignored.

Alterado na versão 3.6: Argumento tzinfo adicionado.

classmethod datetime.strptime(date_string, format)

Return a datetime corresponding to date_string, parsed according to format. This is equivalent to datetime(*(time.strptime(date_string, format)[0:6])). ValueError is raised if the date_string and format can’t be parsed by time.strptime() or if it returns a value which isn’t a time tuple. For a complete list of formatting directives, see Comportamento de strftime() e strptime().

Atributos de classe:

datetime.min

O primeiro datetime representável, datetime(MINYEAR, 1, 1, tzinfo=None).

datetime.max

O último datetime representável, datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999, tzinfo=None).

datetime.resolution

A menor diferença possível entre objetos datetime desiguais, timedelta(microseconds=1).

Atributos de instância (somente leitura):

datetime.year

Entre MINYEAR e MAXYEAR incluindo extremos.

datetime.month

Entre 1 e 12 incluindo extremos.

datetime.day

Entre 1 e o número de dias no mês especificado do ano especificado.

datetime.hour

No intervalo range(24).

datetime.minute

No intervalo range(60).

datetime.second

No intervalo range(60).

datetime.microsecond

No intervalo range(1000000).

datetime.tzinfo

O objeto passado como o argumento tzinfo do construtor datetime, ou None se nada foi passado.

datetime.fold

In [0, 1]. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation.

Novo na versão 3.6.

Operações suportadas:

Operação	Resultado
datetime2 = datetime1 + timedelta	(1)
datetime2 = datetime1 - timedelta	(2)
timedelta = datetime1 - datetime2	(3)
datetime1 < datetime2	Compara um datetime a um datetime. (4)

1. datetime2 is a duration of timedelta removed from datetime1, moving forward in time if timedelta.days > 0, or backward if timedelta.days < 0. The result has the same tzinfo attribute as the input datetime, and datetime2 - datetime1 == timedelta after. OverflowError is raised if datetime2.year would be smaller than MINYEAR or larger than MAXYEAR. Note that no time zone adjustments are done even if the input is an aware object.

2. Computa o datetime2 tal que datetime2 + timedelta == datetime1. Assim como para adição, o resultado tem o mesmo atributo tzinfo que datetime de entrada, e nenhum ajuste de fuso horário é feito mesmo que a entrada seja consciente disso.

3. Subtraction of a datetime from a datetime is defined only if both operands are naive, or if both are aware. If one is aware and the other is naive, TypeError is raised.

   If both are naive, or both are aware and have the same tzinfo attribute, the tzinfo attributes are ignored, and the result is a timedelta object t such that datetime2 + t == datetime1. No time zone adjustments are done in this case.

   If both are aware and have different tzinfo attributes, a-b acts as if a and b were first converted to naive UTC datetimes first. The result is (a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None) - b.utcoffset()) except that the implementation never overflows.

4. datetime1 é considerado menor que datetime2 quando datetime1 precede datetime2 no tempo.

   If one comparand is naive and the other is aware, TypeError is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances.

   If both comparands are aware, and have the same tzinfo attribute, the common tzinfo attribute is ignored and the base datetimes are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset()).

   Alterado na versão 3.3: Equality comparisons between naive and aware datetime instances don’t raise TypeError.

   Nota

   In order to stop comparison from falling back to the default scheme of comparing object addresses, datetime comparison normally raises TypeError if the other comparand isn’t also a datetime object. However, NotImplemented is returned instead if the other comparand has a timetuple() attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a datetime object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively.

datetime objects can be used as dictionary keys. In Boolean contexts, all datetime objects are considered to be true.

Métodos de instância:

datetime.date()

Retorna um objeto date com o mesmo ano, mês e dia.

datetime.time()

Return time object with same hour, minute, second, microsecond and fold. tzinfo is None. See also method timetz().

Alterado na versão 3.6: O valor attr:.fold é copiado ao objeto time retornado.

datetime.timetz()

Return time object with same hour, minute, second, microsecond, fold, and tzinfo attributes. See also method time().

Alterado na versão 3.6: O valor attr:.fold é copiado ao objeto time retornado.

datetime.replace(year=self.year, month=self.month, day=self.day, hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, * fold=0)

Return a datetime with the same attributes, except for those attributes given new values by whichever keyword arguments are specified. Note that tzinfo=None can be specified to create a naive datetime from an aware datetime with no conversion of date and time data.

Novo na versão 3.6: Adicionado o argumento fold.

datetime.astimezone(tz=None)

Retorna um objeto datetime com novo atributo tzinfo definido por tz, ajustando a data e hora de forma que o resultado seja o mesmo horário UTC que self, mas na hora local de tz.

If provided, tz must be an instance of a tzinfo subclass, and its utcoffset() and dst() methods must not return None. If self is naive, it is presumed to represent time in the system timezone.

If called without arguments (or with tz=None) the system local timezone is assumed for the target timezone. The .tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS.

Se self.tzinfo for tz, self.astimezone(tz) é igual a self: nenhum ajuste nos dados de data ou hora é realizado. Caso contrário o resultado é a hora local no fuso horário tz, representando a mesma hora UTC que self: depois astz = dt.astimezone(tz), astz - astz.utcoffset() terá os mesmos dados de data e hora que dt - dt.utcoffset().

If you merely want to attach a time zone object tz to a datetime dt without adjustment of date and time data, use dt.replace(tzinfo=tz). If you merely want to remove the time zone object from an aware datetime dt without conversion of date and time data, use dt.replace(tzinfo=None).

Perceba que o método padrão tzinfo.fromutc() pode ser substituído em uma subclasse tzinfo para afetar o resultado retornado por astimezone(). Ignorando erros de letras maiúsculas/minúsculas, astimezone() funciona como:

def astimezone(self, tz):
    if self.tzinfo is tz:
        return self
    # Convert self to UTC, and attach the new time zone object.
    utc = (self - self.utcoffset()).replace(tzinfo=tz)
    # Convert from UTC to tz's local time.
    return tz.fromutc(utc)

Alterado na versão 3.3: tz agora pode ser omitido.

Alterado na versão 3.6: O método astimezone() agora pode ser chamado em instâncias ingênuas que presumidamente representam a hora local do sistema.

datetime.utcoffset()

If tzinfo is None, returns None, else returns self.tzinfo.utcoffset(self), and raises an exception if the latter doesn’t return None, or a timedelta object representing a whole number of minutes with magnitude less than one day.

datetime.dst()

If tzinfo is None, returns None, else returns self.tzinfo.dst(self), and raises an exception if the latter doesn’t return None, or a timedelta object representing a whole number of minutes with magnitude less than one day.

datetime.tzname()

Se tzinfo for None, retorna None, caso contrário retorna self.tzinfo.tzname(self), levanta uma exceção se o segundo não retornar None ou um objeto string.

datetime.timetuple()

Return a time.struct_time such as returned by time.localtime(). d.timetuple() is equivalent to time.struct_time((d.year, d.month, d.day, d.hour, d.minute, d.second, d.weekday(), yday, dst)), where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st. The tm_isdst flag of the result is set according to the dst() method: tzinfo is None or dst() returns None, tm_isdst is set to -1; else if dst() returns a non-zero value, tm_isdst is set to 1; else tm_isdst is set to 0.

datetime.utctimetuple()

If datetime instance d is naive, this is the same as d.timetuple() except that tm_isdst is forced to 0 regardless of what d.dst() returns. DST is never in effect for a UTC time.

If d is aware, d is normalized to UTC time, by subtracting d.utcoffset(), and a time.struct_time for the normalized time is returned. tm_isdst is forced to 0. Note that an OverflowError may be raised if d.year was MINYEAR or MAXYEAR and UTC adjustment spills over a year boundary.

datetime.toordinal()

Return the proleptic Gregorian ordinal of the date. The same as self.date().toordinal().

datetime.timestamp()

Return POSIX timestamp corresponding to the datetime instance. The return value is a float similar to that returned by time.time().

Naive datetime instances are assumed to represent local time and this method relies on the platform C mktime() function to perform the conversion. Since datetime supports wider range of values than mktime() on many platforms, this method may raise OverflowError for times far in the past or far in the future.

Para instâncias conscientes de datetime, o valor retornado é computado como:

(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()

Novo na versão 3.3.

Alterado na versão 3.6: O método timestamp() usa o atributo fold para desambiguar os tempos durante um intervalo repetido.

Nota

There is no method to obtain the POSIX timestamp directly from a naive datetime instance representing UTC time. If your application uses this convention and your system timezone is not set to UTC, you can obtain the POSIX timestamp by supplying tzinfo=timezone.utc:

timestamp = dt.replace(tzinfo=timezone.utc).timestamp()

ou calculando o timestamp diretamente:

timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)

datetime.weekday()

Retorna o dia da semana como um inteiro, em que segunda-feira é 0 e domingo é 6. O mesmo que self.date().weekday(). Veja também isoweekday().

datetime.isoweekday()

Retorna o dia da semana como um inteiro, em que segunda-feira é 1 e domingo é 7. O mesmo que self.date().isoweekday(). Veja também weekday(), isocalendar().

datetime.isocalendar()

Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The same as self.date().isocalendar().

datetime.isoformat(sep='T', timespec='auto')

Return a string representing the date and time in ISO 8601 format, YYYY-MM-DDTHH:MM:SS.mmmmmm or, if microsecond is 0, YYYY-MM-DDTHH:MM:SS

If utcoffset() does not return None, a 6-character string is appended, giving the UTC offset in (signed) hours and minutes: YYYY-MM-DDTHH:MM:SS.mmmmmm+HH:MM or, if microsecond is 0 YYYY-MM-DDTHH:MM:SS+HH:MM

The optional argument sep (default 'T') is a one-character separator, placed between the date and time portions of the result. For example,

>>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
...     def utcoffset(self, dt): return timedelta(minutes=-399)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'

O argumento opcional timespec especifica o número de componentes adicionais do tempo a incluir (o padrão é 'auto'). Pode ser uma das seguintes strings:

• 'auto': O mesmo que 'seconds' se microsecond é 0, o mesmo que 'microseconds' caso contrário.

• 'hours': Include the hour in the two-digit HH format.

• 'minutes': Include hour and minute in HH:MM format.

• 'seconds': Include hour, minute, and second in HH:MM:SS format.

• 'milliseconds': Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.

• 'microseconds': Include full time in HH:MM:SS.mmmmmm format.

Nota

Componentes do tempo excluídos são truncados, não arredondados.

ValueError será levantado com um argumento timespec inválido.

>>> from datetime import datetime
>>> datetime.now().isoformat(timespec='minutes')
'2002-12-25T00:00'
>>> dt = datetime(2015, 1, 1, 12, 30, 59, 0)
>>> dt.isoformat(timespec='microseconds')
'2015-01-01T12:30:59.000000'

Novo na versão 3.6: Argumento timespec adicionado.

datetime.__str__()

Para uma instância datetime d, str(d) é equivalente a d.isoformat(' ').

datetime.ctime()

Return a string representing the date and time, for example datetime(2002, 12, 4, 20, 30, 40).ctime() == 'Wed Dec  4 20:30:40 2002'. d.ctime() is equivalent to time.ctime(time.mktime(d.timetuple())) on platforms where the native C ctime() function (which time.ctime() invokes, but which datetime.ctime() does not invoke) conforms to the C standard.

datetime.strftime(format)

Return a string representing the date and time, controlled by an explicit format string. For a complete list of formatting directives, see Comportamento de strftime() e strptime().

datetime.__format__(format)

Same as datetime.strftime(). This makes it possible to specify a format string for a datetime object in formatted string literals and when using str.format(). For a complete list of formatting directives, see Comportamento de strftime() e strptime().

Examples of working with datetime objects:

>>> from datetime import datetime, date, time
>>> # Using datetime.combine()
>>> d = date(2005, 7, 14)
>>> t = time(12, 30)
>>> datetime.combine(d, t)
datetime.datetime(2005, 7, 14, 12, 30)
>>> # Using datetime.now() or datetime.utcnow()
>>> datetime.now()   
datetime.datetime(2007, 12, 6, 16, 29, 43, 79043)   # GMT +1
>>> datetime.utcnow()   
datetime.datetime(2007, 12, 6, 15, 29, 43, 79060)
>>> # Using datetime.strptime()
>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")
>>> dt
datetime.datetime(2006, 11, 21, 16, 30)
>>> # Using datetime.timetuple() to get tuple of all attributes
>>> tt = dt.timetuple()
>>> for it in tt:   
...     print(it)
...
2006    # year
11      # month
21      # day
16      # hour
30      # minute
0       # second
1       # weekday (0 = Monday)
325     # number of days since 1st January
-1      # dst - method tzinfo.dst() returned None
>>> # Date in ISO format
>>> ic = dt.isocalendar()
>>> for it in ic:   
...     print(it)
...
2006    # ISO year
47      # ISO week
2       # ISO weekday
>>> # Formatting datetime
>>> dt.strftime("%A, %d. %B %Y %I:%M%p")
'Tuesday, 21. November 2006 04:30PM'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(dt, "day", "month", "time")
'The day is 21, the month is November, the time is 04:30PM.'

Using datetime with tzinfo:

>>> from datetime import timedelta, datetime, tzinfo
>>> class GMT1(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=1) + self.dst(dt)
...     def dst(self, dt):
...         # DST starts last Sunday in March
...         d = datetime(dt.year, 4, 1)   # ends last Sunday in October
...         self.dston = d - timedelta(days=d.weekday() + 1)
...         d = datetime(dt.year, 11, 1)
...         self.dstoff = d - timedelta(days=d.weekday() + 1)
...         if self.dston <=  dt.replace(tzinfo=None) < self.dstoff:
...             return timedelta(hours=1)
...         else:
...             return timedelta(0)
...     def tzname(self,dt):
...          return "GMT +1"
...
>>> class GMT2(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=2) + self.dst(dt)
...     def dst(self, dt):
...         d = datetime(dt.year, 4, 1)
...         self.dston = d - timedelta(days=d.weekday() + 1)
...         d = datetime(dt.year, 11, 1)
...         self.dstoff = d - timedelta(days=d.weekday() + 1)
...         if self.dston <=  dt.replace(tzinfo=None) < self.dstoff:
...             return timedelta(hours=1)
...         else:
...             return timedelta(0)
...     def tzname(self,dt):
...         return "GMT +2"
...
>>> gmt1 = GMT1()
>>> # Daylight Saving Time
>>> dt1 = datetime(2006, 11, 21, 16, 30, tzinfo=gmt1)
>>> dt1.dst()
datetime.timedelta(0)
>>> dt1.utcoffset()
datetime.timedelta(0, 3600)
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=gmt1)
>>> dt2.dst()
datetime.timedelta(0, 3600)
>>> dt2.utcoffset()
datetime.timedelta(0, 7200)
>>> # Convert datetime to another time zone
>>> dt3 = dt2.astimezone(GMT2())
>>> dt3     
datetime.datetime(2006, 6, 14, 14, 0, tzinfo=<GMT2 object at 0x...>)
>>> dt2     
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>)
>>> dt2.utctimetuple() == dt3.utctimetuple()
True

8.1.5. Objetos time

A time object represents a (local) time of day, independent of any particular day, and subject to adjustment via a tzinfo object.

class datetime.time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)

All arguments are optional. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments may be integers, in the following ranges:

• 0 <= hour < 24,

• 0 <= minute < 60,

• 0 <= second < 60,

• 0 <= microsecond < 1000000,

• fold in [0, 1].

If an argument outside those ranges is given, ValueError is raised. All default to 0 except tzinfo, which defaults to None.

Atributos de classe:

time.min

O time mais cedo que pode ser representado, time(0, 0, 0, 0).

time.max

O time mais tardio que pode ser representado, time(23, 59, 59, 999999).

time.resolution

A menor diferença possível entre objetos time diferentes, timedelta(microseconds=1), embora perceba que aritmética sobre objetos time não é suportada.

Atributos de instância (somente leitura):

time.hour

No intervalo range(24).

time.minute

No intervalo range(60).

time.second

No intervalo range(60).

time.microsecond

No intervalo range(1000000).

time.tzinfo

O objeto passado como argumento tzinfo para o construtor da classe time, ou None se nada foi passado.

time.fold

In [0, 1]. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation.

Novo na versão 3.6.

Operações suportadas:

• comparison of time to time, where a is considered less than b when a precedes b in time. If one comparand is naive and the other is aware, TypeError is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances.

  If both comparands are aware, and have the same tzinfo attribute, the common tzinfo attribute is ignored and the base times are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset()). In order to stop mixed-type comparisons from falling back to the default comparison by object address, when a time object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively.

  Alterado na versão 3.3: Equality comparisons between naive and aware time instances don’t raise TypeError.

• hash, use as dict key

• efficient pickling

In boolean contexts, a time object is always considered to be true.

Alterado na versão 3.5: Before Python 3.5, a time object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See bpo-13936 for full details.

Métodos de instância:

time.replace(hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, * fold=0)

Return a time with the same value, except for those attributes given new values by whichever keyword arguments are specified. Note that tzinfo=None can be specified to create a naive time from an aware time, without conversion of the time data.

Novo na versão 3.6: Adicionado o argumento fold.

time.isoformat(timespec='auto')

Return a string representing the time in ISO 8601 format, HH:MM:SS.mmmmmm or, if microsecond is 0, HH:MM:SS If utcoffset() does not return None, a 6-character string is appended, giving the UTC offset in (signed) hours and minutes: HH:MM:SS.mmmmmm+HH:MM or, if self.microsecond is 0, HH:MM:SS+HH:MM

O argumento opcional timespec especifica o número de componentes adicionais do tempo a incluir (o padrão é 'auto'). Pode ser uma das seguintes strings:

• 'auto': O mesmo que 'seconds' se microsecond é 0, o mesmo que 'microseconds' caso contrário.

• 'hours': Include the hour in the two-digit HH format.

• 'minutes': Include hour and minute in HH:MM format.

• 'seconds': Include hour, minute, and second in HH:MM:SS format.

• 'milliseconds': Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.

• 'microseconds': Include full time in HH:MM:SS.mmmmmm format.

Nota

Componentes do tempo excluídos são truncados, não arredondados.

ValueError será levantado com um argumento timespec inválido.

>>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
'12:34'
>>> dt = time(hour=12, minute=34, second=56, microsecond=0)
>>> dt.isoformat(timespec='microseconds')
'12:34:56.000000'
>>> dt.isoformat(timespec='auto')
'12:34:56'

Novo na versão 3.6: Argumento timespec adicionado.

time.__str__()

Para um tempo t, str(t) é equivalente a t.isoformat().

time.strftime(format)

Return a string representing the time, controlled by an explicit format string. For a complete list of formatting directives, see Comportamento de strftime() e strptime().

time.__format__(format)

Same as time.strftime(). This makes it possible to specify a format string for a time object in formatted string literals and when using str.format(). For a complete list of formatting directives, see Comportamento de strftime() e strptime().

time.utcoffset()

If tzinfo is None, returns None, else returns self.tzinfo.utcoffset(None), and raises an exception if the latter doesn’t return None or a timedelta object representing a whole number of minutes with magnitude less than one day.

time.dst()

If tzinfo is None, returns None, else returns self.tzinfo.dst(None), and raises an exception if the latter doesn’t return None, or a timedelta object representing a whole number of minutes with magnitude less than one day.

time.tzname()

Se tzinfo for None, retorna None, caso contrário retorna self.tzinfo.tzname(None), ou levanta uma exceção se o último caso não retornar None ou um objeto string.

Exemplo:

>>> from datetime import time, tzinfo, timedelta
>>> class GMT1(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=1)
...     def dst(self, dt):
...         return timedelta(0)
...     def tzname(self,dt):
...         return "Europe/Prague"
...
>>> t = time(12, 10, 30, tzinfo=GMT1())
>>> t                               
datetime.time(12, 10, 30, tzinfo=<GMT1 object at 0x...>)
>>> gmt = GMT1()
>>> t.isoformat()
'12:10:30+01:00'
>>> t.dst()
datetime.timedelta(0)
>>> t.tzname()
'Europe/Prague'
>>> t.strftime("%H:%M:%S %Z")
'12:10:30 Europe/Prague'
>>> 'The {} is {:%H:%M}.'.format("time", t)
'The time is 12:10.'

8.1.6. Objetos tzinfo

class datetime.tzinfo

This is an abstract base class, meaning that this class should not be instantiated directly. You need to derive a concrete subclass, and (at least) supply implementations of the standard tzinfo methods needed by the datetime methods you use. The datetime module supplies a simple concrete subclass of tzinfo, timezone, which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT.

Uma instância de (uma subclasse concreta de) tzinfo pode ser passada para os construtores de objetos datetime e time. Os objetos time veem seus atributos como se estivessem em horário local, e o objeto tzinfo suporta métodos revelando a diferença da hora local a partir de UTC, o nome do fuso horário, e diferença de horário em horário de verão, todos relativos ao objeto date ou time passado para eles.

Special requirement for pickling: A tzinfo subclass must have an __init__() method that can be called with no arguments, else it can be pickled but possibly not unpickled again. This is a technical requirement that may be relaxed in the future.

A concrete subclass of tzinfo may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware datetime objects. If in doubt, simply implement all of them.

tzinfo.utcoffset(dt)

Return offset of local time from UTC, in minutes east of UTC. If local time is west of UTC, this should be negative. Note that this is intended to be the total offset from UTC; for example, if a tzinfo object represents both time zone and DST adjustments, utcoffset() should return their sum. If the UTC offset isn’t known, return None. Else the value returned must be a timedelta object specifying a whole number of minutes in the range -1439 to 1439 inclusive (1440 = 24*60; the magnitude of the offset must be less than one day). Most implementations of utcoffset() will probably look like one of these two:

return CONSTANT                 # fixed-offset class
return CONSTANT + self.dst(dt)  # daylight-aware class

Se utcoffset() não retorna None, dst() também não deve retornar None.

A implementação padrão de utcoffset() levanta NotImplementedError.

tzinfo.dst(dt)

Return the daylight saving time (DST) adjustment, in minutes east of UTC, or None if DST information isn’t known. Return timedelta(0) if DST is not in effect. If DST is in effect, return the offset as a timedelta object (see utcoffset() for details). Note that DST offset, if applicable, has already been added to the UTC offset returned by utcoffset(), so there’s no need to consult dst() unless you’re interested in obtaining DST info separately. For example, datetime.timetuple() calls its tzinfo attribute’s dst() method to determine how the tm_isdst flag should be set, and tzinfo.fromutc() calls dst() to account for DST changes when crossing time zones.

Uma instância tz de uma subclasse tzinfo que modela tanto horário padrão quanto horário de verão deve ser consistente neste sentido:

tz.utcoffset(dt) - tz.dst(dt)

must return the same result for every datetime dt with dt.tzinfo == tz For sane tzinfo subclasses, this expression yields the time zone’s “standard offset”, which should not depend on the date or the time, but only on geographic location. The implementation of datetime.astimezone() relies on this, but cannot detect violations; it’s the programmer’s responsibility to ensure it. If a tzinfo subclass cannot guarantee this, it may be able to override the default implementation of tzinfo.fromutc() to work correctly with astimezone() regardless.

Maior parte das implementações de dst() provavelmente irá parecer com um destes dois:

def dst(self, dt):
    # a fixed-offset class:  doesn't account for DST
    return timedelta(0)

ou

def dst(self, dt):
    # Code to set dston and dstoff to the time zone's DST
    # transition times based on the input dt.year, and expressed
    # in standard local time.  Then

    if dston <= dt.replace(tzinfo=None) < dstoff:
        return timedelta(hours=1)
    else:
        return timedelta(0)

A implementação padrão de dst() levanta NotImplementedError.

tzinfo.tzname(dt)

Return the time zone name corresponding to the datetime object dt, as a string. Nothing about string names is defined by the datetime module, and there’s no requirement that it mean anything in particular. For example, “GMT”, “UTC”, “-500”, “-5:00”, “EDT”, “US/Eastern”, “America/New York” are all valid replies. Return None if a string name isn’t known. Note that this is a method rather than a fixed string primarily because some tzinfo subclasses will wish to return different names depending on the specific value of dt passed, especially if the tzinfo class is accounting for daylight time.

A implementação padrão de tzname() levanta NotImplementedError.

These methods are called by a datetime or time object, in response to their methods of the same names. A datetime object passes itself as the argument, and a time object passes None as the argument. A tzinfo subclass’s methods should therefore be prepared to accept a dt argument of None, or of class datetime.

When None is passed, it’s up to the class designer to decide the best response. For example, returning None is appropriate if the class wishes to say that time objects don’t participate in the tzinfo protocols. It may be more useful for utcoffset(None) to return the standard UTC offset, as there is no other convention for discovering the standard offset.

When a datetime object is passed in response to a datetime method, dt.tzinfo is the same object as self. tzinfo methods can rely on this, unless user code calls tzinfo methods directly. The intent is that the tzinfo methods interpret dt as being in local time, and not need worry about objects in other timezones.

Exste mais um método tzinfo que uma subclasse pode querer substituir:

tzinfo.fromutc(dt)

This is called from the default datetime.astimezone() implementation. When called from that, dt.tzinfo is self, and dt’s date and time data are to be viewed as expressing a UTC time. The purpose of fromutc() is to adjust the date and time data, returning an equivalent datetime in self’s local time.

Most tzinfo subclasses should be able to inherit the default fromutc() implementation without problems. It’s strong enough to handle fixed-offset time zones, and time zones accounting for both standard and daylight time, and the latter even if the DST transition times differ in different years. An example of a time zone the default fromutc() implementation may not handle correctly in all cases is one where the standard offset (from UTC) depends on the specific date and time passed, which can happen for political reasons. The default implementations of astimezone() and fromutc() may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes.

Ignorando o código para casos de erros, a implementação padrão fromutc() funciona como:

def fromutc(self, dt):
    # raise ValueError error if dt.tzinfo is not self
    dtoff = dt.utcoffset()
    dtdst = dt.dst()
    # raise ValueError if dtoff is None or dtdst is None
    delta = dtoff - dtdst  # this is self's standard offset
    if delta:
        dt += delta   # convert to standard local time
        dtdst = dt.dst()
        # raise ValueError if dtdst is None
    if dtdst:
        return dt + dtdst
    else:
        return dt

Example tzinfo classes:

from datetime import tzinfo, timedelta, datetime, timezone

ZERO = timedelta(0)
HOUR = timedelta(hours=1)
SECOND = timedelta(seconds=1)

# A class capturing the platform's idea of local time.
# (May result in wrong values on historical times in
#  timezones where UTC offset and/or the DST rules had
#  changed in the past.)
import time as _time

STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
    DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
    DSTOFFSET = STDOFFSET

DSTDIFF = DSTOFFSET - STDOFFSET

class LocalTimezone(tzinfo):

    def fromutc(self, dt):
        assert dt.tzinfo is self
        stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND
        args = _time.localtime(stamp)[:6]
        dst_diff = DSTDIFF // SECOND
        # Detect fold
        fold = (args == _time.localtime(stamp - dst_diff))
        return datetime(*args, microsecond=dt.microsecond,
                        tzinfo=self, fold=fold)

    def utcoffset(self, dt):
        if self._isdst(dt):
            return DSTOFFSET
        else:
            return STDOFFSET

    def dst(self, dt):
        if self._isdst(dt):
            return DSTDIFF
        else:
            return ZERO

    def tzname(self, dt):
        return _time.tzname[self._isdst(dt)]

    def _isdst(self, dt):
        tt = (dt.year, dt.month, dt.day,
              dt.hour, dt.minute, dt.second,
              dt.weekday(), 0, 0)
        stamp = _time.mktime(tt)
        tt = _time.localtime(stamp)
        return tt.tm_isdst > 0

Local = LocalTimezone()


# A complete implementation of current DST rules for major US time zones.

def first_sunday_on_or_after(dt):
    days_to_go = 6 - dt.weekday()
    if days_to_go:
        dt += timedelta(days_to_go)
    return dt


# US DST Rules
#
# This is a simplified (i.e., wrong for a few cases) set of rules for US
# DST start and end times. For a complete and up-to-date set of DST rules
# and timezone definitions, visit the Olson Database (or try pytz):
# http://www.twinsun.com/tz/tz-link.htm
# http://sourceforge.net/projects/pytz/ (might not be up-to-date)
#
# In the US, since 2007, DST starts at 2am (standard time) on the second
# Sunday in March, which is the first Sunday on or after Mar 8.
DSTSTART_2007 = datetime(1, 3, 8, 2)
# and ends at 2am (DST time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 2)
# From 1987 to 2006, DST used to start at 2am (standard time) on the first
# Sunday in April and to end at 2am (DST time) on the last
# Sunday of October, which is the first Sunday on or after Oct 25.
DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
DSTEND_1987_2006 = datetime(1, 10, 25, 2)
# From 1967 to 1986, DST used to start at 2am (standard time) on the last
# Sunday in April (the one on or after April 24) and to end at 2am (DST time)
# on the last Sunday of October, which is the first Sunday
# on or after Oct 25.
DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
DSTEND_1967_1986 = DSTEND_1987_2006

def us_dst_range(year):
    # Find start and end times for US DST. For years before 1967, return
    # start = end for no DST.
    if 2006 < year:
        dststart, dstend = DSTSTART_2007, DSTEND_2007
    elif 1986 < year < 2007:
        dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
    elif 1966 < year < 1987:
        dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
    else:
        return (datetime(year, 1, 1), ) * 2

    start = first_sunday_on_or_after(dststart.replace(year=year))
    end = first_sunday_on_or_after(dstend.replace(year=year))
    return start, end


class USTimeZone(tzinfo):

    def __init__(self, hours, reprname, stdname, dstname):
        self.stdoffset = timedelta(hours=hours)
        self.reprname = reprname
        self.stdname = stdname
        self.dstname = dstname

    def __repr__(self):
        return self.reprname

    def tzname(self, dt):
        if self.dst(dt):
            return self.dstname
        else:
            return self.stdname

    def utcoffset(self, dt):
        return self.stdoffset + self.dst(dt)

    def dst(self, dt):
        if dt is None or dt.tzinfo is None:
            # An exception may be sensible here, in one or both cases.
            # It depends on how you want to treat them.  The default
            # fromutc() implementation (called by the default astimezone()
            # implementation) passes a datetime with dt.tzinfo is self.
            return ZERO
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        # Can't compare naive to aware objects, so strip the timezone from
        # dt first.
        dt = dt.replace(tzinfo=None)
        if start + HOUR <= dt < end - HOUR:
            # DST is in effect.
            return HOUR
        if end - HOUR <= dt < end:
            # Fold (an ambiguous hour): use dt.fold to disambiguate.
            return ZERO if dt.fold else HOUR
        if start <= dt < start + HOUR:
            # Gap (a non-existent hour): reverse the fold rule.
            return HOUR if dt.fold else ZERO
        # DST is off.
        return ZERO

    def fromutc(self, dt):
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        start = start.replace(tzinfo=self)
        end = end.replace(tzinfo=self)
        std_time = dt + self.stdoffset
        dst_time = std_time + HOUR
        if end <= dst_time < end + HOUR:
            # Repeated hour
            return std_time.replace(fold=1)
        if std_time < start or dst_time >= end:
            # Standard time
            return std_time
        if start <= std_time < end - HOUR:
            # Daylight saving time
            return dst_time


Eastern  = USTimeZone(-5, "Eastern",  "EST", "EDT")
Central  = USTimeZone(-6, "Central",  "CST", "CDT")
Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
Pacific  = USTimeZone(-8, "Pacific",  "PST", "PDT")

Note that there are unavoidable subtleties twice per year in a tzinfo subclass accounting for both standard and daylight time, at the DST transition points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the minute after 1:59 (EST) on the second Sunday in March, and ends the minute after 1:59 (EDT) on the first Sunday in November:

  UTC   3:MM  4:MM  5:MM  6:MM  7:MM  8:MM
  EST  22:MM 23:MM  0:MM  1:MM  2:MM  3:MM
  EDT  23:MM  0:MM  1:MM  2:MM  3:MM  4:MM

start  22:MM 23:MM  0:MM  1:MM  3:MM  4:MM

  end  23:MM  0:MM  1:MM  1:MM  2:MM  3:MM

When DST starts (the “start” line), the local wall clock leaps from 1:59 to 3:00. A wall time of the form 2:MM doesn’t really make sense on that day, so astimezone(Eastern) won’t deliver a result with hour == 2 on the day DST begins. For example, at the Spring forward transition of 2016, we get

>>> u0 = datetime(2016, 3, 13, 5, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname())
...
05:00:00 UTC = 00:00:00 EST
06:00:00 UTC = 01:00:00 EST
07:00:00 UTC = 03:00:00 EDT
08:00:00 UTC = 04:00:00 EDT

When DST ends (the “end” line), there’s a potentially worse problem: there’s an hour that can’t be spelled unambiguously in local wall time: the last hour of daylight time. In Eastern, that’s times of the form 5:MM UTC on the day daylight time ends. The local wall clock leaps from 1:59 (daylight time) back to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous. astimezone() mimics the local clock’s behavior by mapping two adjacent UTC hours into the same local hour then. In the Eastern example, UTC times of the form 5:MM and 6:MM both map to 1:MM when converted to Eastern, but earlier times have the fold attribute set to 0 and the later times have it set to 1. For example, at the Fall back transition of 2016, we get

>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0

Note that the datetime instances that differ only by the value of the fold attribute are considered equal in comparisons.

Aplicações que não podem suportar horário na parede com ambiguidades devem explicitamente verificar o valor do atributo fold ou evitar o uso de subclasses tzinfo híbridas; não existem ambiguidades ao usar timezone, ou qualquer outra subclasse tzinfo com diferença fixa (tal como uma classe representando apenas o horário padrão na costa leste EST (diferença fixa de -5 horas), ou apenas o horário de verão na costa leste EDT (diferença fixa de -4 horas)).

Ver também

dateutil.tz

The standard library has timezone class for handling arbitrary fixed offsets from UTC and timezone.utc as UTC timezone instance.

dateutil.tz library brings the IANA timezone database (also known as the Olson database) to Python and its usage is recommended.

Base de dados de fusos horários IANA

O banco de dados de fuso horário (comumente chando de tz, tzdata ou zoneinfo) contém código e dados que representam o histórico de hora local para muitas localizações representativas ao redor do globo. Ele é atualizado periodicamente para refletir mudanças feitas por corpos políticos para limites de fuso horário, diferenças UTC, e regras de horário de verão.

8.1.7. Objetos timezone

The timezone class is a subclass of tzinfo, each instance of which represents a timezone defined by a fixed offset from UTC. Note that objects of this class cannot be used to represent timezone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time.

class datetime.timezone(offset, name=None)

The offset argument must be specified as a timedelta object representing the difference between the local time and UTC. It must be strictly between -timedelta(hours=24) and timedelta(hours=24) and represent a whole number of minutes, otherwise ValueError is raised.

The name argument is optional. If specified it must be a string that will be used as the value returned by the datetime.tzname() method.

Novo na versão 3.2.

timezone.utcoffset(dt)

Return the fixed value specified when the timezone instance is constructed. The dt argument is ignored. The return value is a timedelta instance equal to the difference between the local time and UTC.

timezone.tzname(dt)

Return the fixed value specified when the timezone instance is constructed. If name is not provided in the constructor, the name returned by tzname(dt) is generated from the value of the offset as follows. If offset is timedelta(0), the name is “UTC”, otherwise it is a string ‘UTC±HH:MM’, where ± is the sign of offset, HH and MM are two digits of offset.hours and offset.minutes respectively.

Alterado na versão 3.6: Name generated from offset=timedelta(0) is now plain ‘UTC’, not ‘UTC+00:00’.

timezone.dst(dt)

Sempre retorna None.

timezone.fromutc(dt)

Return dt + offset. The dt argument must be an aware datetime instance, with tzinfo set to self.

Atributos de classe:

timezone.utc

O fuso horário UTC, timezone(timedelta(0)).

8.1.8. Comportamento de strftime() e strptime()

date, datetime, and time objects all support a strftime(format) method, to create a string representing the time under the control of an explicit format string. Broadly speaking, d.strftime(fmt) acts like the time module’s time.strftime(fmt, d.timetuple()) although not all objects support a timetuple() method.

Conversely, the datetime.strptime() class method creates a datetime object from a string representing a date and time and a corresponding format string. datetime.strptime(date_string, format) is equivalent to datetime(*(time.strptime(date_string, format)[0:6])), except when the format includes sub-second components or timezone offset information, which are supported in datetime.strptime but are discarded by time.strptime.

For time objects, the format codes for year, month, and day should not be used, as time objects have no such values. If they’re used anyway, 1900 is substituted for the year, and 1 for the month and day.

For date objects, the format codes for hours, minutes, seconds, and microseconds should not be used, as date objects have no such values. If they’re used anyway, 0 is substituted for them.

The full set of format codes supported varies across platforms, because Python calls the platform C library’s strftime() function, and platform variations are common. To see the full set of format codes supported on your platform, consult the strftime(3) documentation.

The following is a list of all the format codes that the C standard (1989 version) requires, and these work on all platforms with a standard C implementation. Note that the 1999 version of the C standard added additional format codes.

Diretiva	Significado	Exemplo	Notas
%a	Dias da semana como nomes abreviados da localidade.	Sun, Mon, …, Sat (en_US); So, Mo, …, Sa (de_DE)	(1)
%A	Dia da semana como nome completo da localidade.	Sunday, Monday, …, Saturday (en_US); Sonntag, Montag, …, Samstag (de_DE)	(1)
%w	Dia da semana como um número decimal, onde 0 é domingo e 6 é sábado.	0, 1, …, 6
%d	Dia do mês como um número decimal com zeros a esquerda.	01, 02, …, 31
%b	Mês como nome da localidade abreviado.	Jan, Feb, …, Dec (en_US); Jan, Feb, …, Dez (de_DE)	(1)
%B	Mês como nome completo da localidade.	January, February, …, December (en_US); janeiro, fevereiro, …, dezembro (pt_BR)	(1)
%m	Mês como um número decimal com zeros a esquerda.	01, 02, …, 12
%y	Ano sem século como um número decimal com zeros a esquerda.	00, 01, …, 99
%Y	Ano com o século como um número decimal.	0001, 0002, …, 2013, 2014, …, 9998, 9999	(2)
%H	Hora (relógio de 24 horas) como um número decimal com zeros a esquerda.	00, 01, …, 23
%I	Hora (relógio de 12 horas) como um número decimal com zeros a esquerda.	01, 02, …, 12
%p	Equivalente da localidade a AM ou PM.	AM, PM (en_US); am, pm (de_DE)	(1), (3)
%M	Minutos como um número decimal, com zeros a esquerda.	00, 01, …, 59
%S	Segundos como um número decimal, com zeros a esquerda.	00, 01, …, 59	(4)
%f	Micro-segundos como um número decimal, com zeros a esquerda.	000000, 000001, …, 999999	(5)
%z	UTC offset in the form +HHMM or -HHMM (empty string if the object is naive).	(empty), +0000, -0400, +1030	(6)
%Z	Nome do fuso horário (string vazia se o objeto é ingênuo).	(empty), UTC, EST, CST
%j	Dia do ano como um número decimal, com zeros a esquerda.	001, 002, …, 366
%U	Número da semana do ano (Domingo como o primeiro dia da semana) como um número decimal, com zeros a esquerda. Todos os dias em um ano novo precedendo o primeiro domingo são considerados como estando na semana 0.	00, 01, …, 53	(7)
%W	Número da semana do ano (Segunda-feira como o primeiro dia da semana) como um número decimal. Todos os dias em um ano novo precedendo a primeira segunda-feira são considerados como estando na semana 0.	00, 01, …, 53	(7)
%c	Representação de data e hora apropriada da localidade.	Tue Aug 16 21:30:00 1988 (en_US); Di 16 Aug 21:30:00 1988 (de_DE)	(1)
%x	Representação de data apropriada de localidade.	08/16/88 (None); 08/16/1988 (en_US); 16.08.1988 (de_DE)	(1)
%X	Representação de hora apropriada da localidade.	21:30:00 (en_US); 21:30:00 (de_DE)	(1)
%%	Um caractere literal '%'.	%

Several additional directives not required by the C89 standard are included for convenience. These parameters all correspond to ISO 8601 date values. These may not be available on all platforms when used with the strftime() method. The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above. Calling strptime() with incomplete or ambiguous ISO 8601 directives will raise a ValueError.

Diretiva	Significado	Exemplo	Notas
%G	Ano ISO 8601 com o século representando o ano que a maior parte da semana ISO (%V).	0001, 0002, …, 2013, 2014, …, 9998, 9999	(8)
%u	Dia de semana ISO 8601 como um número decimal onde 1 é segunda-feira.	1, 2, …, 7
%V	Semana ISO 8601 como um número decimal, com segunda-feira como o primeiro dia da semana. A semana 01 é a semana contendo o dia 4 de Janeiro.	01, 02, …, 53	(8)

Novo na versão 3.6: %G, %u e %V foram adicionados.

Notas:

1. Devido ao fato que o formato depende da localidade atual, deve-se tomar cuidado ao fazer suposições sobre o valor na saída. Ordenamento de campos irá variar (por exemplo, “mês/dia/ano” versus “dia/mês/ano”), e a saída pode conter caracteres Unicode que foram codificados usando a codificação padrão da localidade (por exemplo, se a localidade atual é ja_JP, a codificação padrão pode ser qualquer uma dentre eucJP, SJIS, ou utf-8; utilize locale.getlocale() para determinar a codificação atual da localidade).

2. O método strptime() pode interpretar anos no intervalo [1, 9999], mas anos < 1000 devem ser preenchidos com 0 para ter 4 dígitos de extensão.

   Alterado na versão 3.2: Em versões anteriores, o método strftime() era restrito a anos>= 1900.

   Alterado na versão 3.3: Na versão 3.2, o método strftime() era restrito a anos >= 1000.

3. Quando usado com o método strptime(), a diretiva %p apenas afeta as horas na saída se a diretiva %I é usada para analisar a hora.

4. Ao contrário do módulo time, o módulo datetime não suporta segundos bissextos.

5. When used with the strptime() method, the %f directive accepts from one to six digits and zero pads on the right. %f is an extension to the set of format characters in the C standard (but implemented separately in datetime objects, and therefore always available).

6. Para um objeto ingênuo, os códigos de formatação %z e %Z são substituídos por strings vazias.

   Para um objeto consciente:

   %z

   utcoffset() is transformed into a 5-character string of the form +HHMM or -HHMM, where HH is a 2-digit string giving the number of UTC offset hours, and MM is a 2-digit string giving the number of UTC offset minutes. For example, if utcoffset() returns timedelta(hours=-3, minutes=-30), %z is replaced with the string '-0330'.

   %Z

   If tzname() returns None, %Z is replaced by an empty string. Otherwise %Z is replaced by the returned value, which must be a string.

   Alterado na versão 3.2: When the %z directive is provided to the strptime() method, an aware datetime object will be produced. The tzinfo of the result will be set to a timezone instance.

7. Quando for usado com o método strptime(), %U e %W são apenas usados em cálculos quando o dia da semana e o ano do calendário (%Y) são especificados.

8. Similar a %U e %W, %V é apenas usado em cálculos quando o dia da semana e o ano ISO (%G) são especificados em uma string de formatação strptime(). Perceba também que %G e %Y não são intercambiáveis.

Notas de rodapé

1

Se, isto é, nós ignoramos os efeitos da Relatividade