8.1. datetime
— Basic date and time types¶
Source code: Lib/datetime.py
The datetime
module supplies classes for manipulating dates and times in
both simple and complex ways. While date and time arithmetic is supported, the
focus of the implementation is on efficient attribute extraction for output
formatting and manipulation. For related functionality, see also the
time
and calendar
modules.
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.
The datetime
module exports the following constants:
Ver también
8.1.1. Available Types¶
-
class
datetime.
date
An idealized naive date, assuming the current Gregorian calendar always was, and always will be, in effect. Attributes:
year
,month
, andday
.
-
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
, andtzinfo
.
-
class
datetime.
datetime
A combination of a date and a time. Attributes:
year
,month
,day
,hour
,minute
,second
,microsecond
, andtzinfo
.
-
class
datetime.
timedelta
A duration expressing the difference between two
date
,time
, ordatetime
instances to microsecond resolution.
-
class
datetime.
tzinfo
An abstract base class for time zone information objects. These are used by the
datetime
andtime
classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time).
-
class
datetime.
timezone
A class that implements the
tzinfo
abstract base class as a fixed offset from the UTC.Nuevo en la versión 3.2.
Objects of these types are immutable.
Objects of the date
type are always naive.
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.
Subclass relationships:
object
timedelta
tzinfo
timezone
time
date
datetime
8.1.2. timedelta
Objects¶
A timedelta
object represents a duration, the difference between two
dates or times.
-
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:
- A millisecond is converted to 1000 microseconds.
- A minute is converted to 60 seconds.
- An hour is converted to 3600 seconds.
- A week is converted to 7 days.
and days, seconds and microseconds are then normalized so that the representation is unique, with
0 <= microseconds < 1000000
0 <= seconds < 3600*24
(the number of seconds in one day)-999999999 <= days <= 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).
If the normalized value of days lies outside the indicated range,
OverflowError
is raised.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.
max
¶ The most positive
timedelta
object,timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999)
.
-
timedelta.
resolution
¶ The smallest possible difference between non-equal
timedelta
objects,timedelta(microseconds=1)
.
Note that, because of normalization, timedelta.max
> -timedelta.min
.
-timedelta.max
is not representable as a timedelta
object.
Instance attributes (read-only):
Attribute | Value |
---|---|
days |
Between -999999999 and 999999999 inclusive |
seconds |
Between 0 and 86399 inclusive |
microseconds |
Between 0 and 999999 inclusive |
Supported operations:
Operation | Result |
---|---|
t1 = t2 + t3 |
Sum of t2 and t3. Afterwards t1-t2 == t3 and t1-t3 == t2 are true. (1) |
t1 = t2 - t3 |
Difference of t2 and t3. Afterwards t1 == t2 - t3 and t2 == t1 + t3 are true. (1) |
t1 = t2 * i or t1 = i * t2 |
Delta multiplied by an integer.
Afterwards t1 // i == t2 is true,
provided i != 0 . |
In general, t1 * i == t1 * (i-1) + t1 is true. (1) | |
t1 = t2 * f or t1 = f * t2 |
Delta multiplied by a float. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even. |
f = t2 / t3 |
Division (3) of t2 by t3. Returns a
float object. |
t1 = t2 / f or t1 = t2 / i |
Delta divided by a float or an int. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even. |
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 |
The remainder is computed as a
timedelta object. (3) |
q, r = divmod(t1, t2) |
Computes the quotient and the remainder:
q = t1 // t2 (3) and r = t1 % t2 .
q is an integer and r is a timedelta
object. |
+t1 |
Returns a timedelta object with the
same value. (2) |
-t1 |
equivalent to timedelta (-t1.days, -t1.seconds,
-t1.microseconds), and to t1* -1. (1)(4) |
abs(t) |
equivalent to +t when t.days >= 0 , and
to -t when t.days < 0 . (2) |
str(t) |
Returns a string in the form
[D day[s], ][H]H:MM:SS[.UUUUUU] , where D
is negative for negative t . (5) |
repr(t) |
Returns a string in the form
datetime.timedelta(D[, S[, U]]) , where D
is negative for negative t . (5) |
Notes:
This is exact, but may overflow.
This is exact, and cannot overflow.
Division by 0 raises
ZeroDivisionError
.-timedelta.max is not representable as a
timedelta
object.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
In addition to the operations listed above timedelta
objects support
certain additions and subtractions with date
and datetime
objects (see below).
Distinto en la versión 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)
.
Instance methods:
-
timedelta.
total_seconds
()¶ Return the total number of seconds contained in the duration. Equivalent to
td / timedelta(seconds=1)
.Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy.
Nuevo en la versión 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
Objects¶
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
If an argument outside those ranges is given,
ValueError
is raised.
Other constructors, all class methods:
-
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 raiseOverflowError
, if the timestamp is out of the range of values supported by the platform Clocaltime()
function, andOSError
onlocaltime()
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 byfromtimestamp()
.Distinto en la versión 3.3: Raise
OverflowError
instead ofValueError
if the timestamp is out of the range of values supported by the platform Clocaltime()
function. RaiseOSError
instead ofValueError
onlocaltime()
failure.
-
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 unless1 <= ordinal <= date.max.toordinal()
. For any date d,date.fromordinal(d.toordinal()) == d
.
Class attributes:
-
date.
min
¶ The earliest representable date,
date(MINYEAR, 1, 1)
.
-
date.
max
¶ The latest representable date,
date(MAXYEAR, 12, 31)
.
-
date.
resolution
¶ The smallest possible difference between non-equal date objects,
timedelta(days=1)
.
Instance attributes (read-only):
-
date.
month
¶ Between 1 and 12 inclusive.
-
date.
day
¶ Between 1 and the number of days in the given month of the given year.
Supported operations:
Operation | Result |
---|---|
date2 = date1 + timedelta |
date2 is timedelta.days days removed
from date1. (1) |
date2 = date1 - timedelta |
Computes date2 such that date2 +
timedelta == date1 . (2) |
timedelta = date1 - date2 |
(3) |
date1 < date2 |
date1 is considered less than date2 when date1 precedes date2 in time. (4) |
Notes:
- date2 is moved forward in time if
timedelta.days > 0
, or backward iftimedelta.days < 0
. Afterwarddate2 - date1 == timedelta.days
.timedelta.seconds
andtimedelta.microseconds
are ignored.OverflowError
is raised ifdate2.year
would be smaller thanMINYEAR
or larger thanMAXYEAR
. - This isn’t quite equivalent to date1 + (-timedelta), because -timedelta in
isolation can overflow in cases where date1 - timedelta does not.
timedelta.seconds
andtimedelta.microseconds
are ignored. - This is exact, and cannot overflow. timedelta.seconds and timedelta.microseconds are 0, and date2 + timedelta == date1 after.
- In other words,
date1 < date2
if and only ifdate1.toordinal() < date2.toordinal()
. In order to stop comparison from falling back to the default scheme of comparing object addresses, date comparison normally raisesTypeError
if the other comparand isn’t also adate
object. However,NotImplemented
is returned instead if the other comparand has atimetuple()
attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when adate
object is compared to an object of a different type,TypeError
is raised unless the comparison is==
or!=
. The latter cases returnFalse
orTrue
, respectively.
Dates can be used as dictionary keys. In Boolean contexts, all date
objects are considered to be true.
Instance methods:
-
date.
replace
(year, month, 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)
, thend.replace(day=26) == date(2002, 12, 26)
.
-
date.
timetuple
()¶ Return a
time.struct_time
such as returned bytime.localtime()
. The hours, minutes and seconds are 0, and the DST flag is -1.d.timetuple()
is equivalent totime.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))
, whereyday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1
is the day number within the current year starting with1
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
()¶ Return the day of the week as an integer, where Monday is 0 and Sunday is 6. For example,
date(2002, 12, 4).weekday() == 2
, a Wednesday. See alsoisoweekday()
.
-
date.
isoweekday
()¶ Return the day of the week as an integer, where Monday is 1 and Sunday is 7. For example,
date(2002, 12, 4).isoweekday() == 3
, a Wednesday. See alsoweekday()
,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)
anddate(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__
()¶ For a date d,
str(d)
is equivalent tod.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 totime.ctime(time.mktime(d.timetuple()))
on platforms where the native Cctime()
function (whichtime.ctime()
invokes, but whichdate.ctime()
does not invoke) conforms to the C standard.
-
date.
strftime
(format)¶ Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values. For a complete list of formatting directives, see strftime() and strptime() Behavior.
-
date.
__format__
(format)¶ Same as
date.strftime()
. This makes it possible to specify a format string for adate
object when usingstr.format()
. For a complete list of formatting directives, see strftime() and strptime() Behavior.
Example of counting days to an event:
>>> 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. datetime
Objects¶
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.
Constructor:
-
class
datetime.
datetime
(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None)¶ The year, month and day arguments are required. tzinfo may be
None
, or an instance of atzinfo
subclass. The remaining 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
0 <= hour < 24
0 <= minute < 60
0 <= second < 60
0 <= microsecond < 1000000
If an argument outside those ranges is given,
ValueError
is raised.
Other constructors, all class methods:
-
classmethod
datetime.
today
()¶ Return the current local datetime, with
tzinfo
None
. This is equivalent todatetime.fromtimestamp(time.time())
. See alsonow()
,fromtimestamp()
.
-
classmethod
datetime.
now
(tz=None)¶ Return the current local date and time. If optional argument tz is
None
or not specified, this is liketoday()
, but, if possible, supplies more precision than can be gotten from going through atime.time()
timestamp (for example, this may be possible on platforms supplying the Cgettimeofday()
function).If tz is not
None
, it must be an instance of atzinfo
subclass, and the current date and time are converted to tz’s time zone. In this case the result is equivalent totz.fromutc(datetime.utcnow().replace(tzinfo=tz))
. See alsotoday()
,utcnow()
.
-
classmethod
datetime.
utcnow
()¶ Return the current UTC date and time, with
tzinfo
None
. This is likenow()
, but returns the current UTC date and time, as a naivedatetime
object. An aware current UTC datetime can be obtained by callingdatetime.now(timezone.utc)
. See alsonow()
.
-
classmethod
datetime.
fromtimestamp
(timestamp, tz=None)¶ Return the local date and time corresponding to the POSIX timestamp, such as is returned by
time.time()
. If optional argument tz isNone
or not specified, the timestamp is converted to the platform’s local date and time, and the returneddatetime
object is naive.If tz is not
None
, it must be an instance of atzinfo
subclass, and the timestamp is converted to tz’s time zone. In this case the result is equivalent totz.fromutc(datetime.utcfromtimestamp(timestamp).replace(tzinfo=tz))
.fromtimestamp()
may raiseOverflowError
, if the timestamp is out of the range of values supported by the platform Clocaltime()
orgmtime()
functions, andOSError
onlocaltime()
orgmtime()
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 byfromtimestamp()
, and then it’s possible to have two timestamps differing by a second that yield identicaldatetime
objects. See alsoutcfromtimestamp()
.Distinto en la versión 3.3: Raise
OverflowError
instead ofValueError
if the timestamp is out of the range of values supported by the platform Clocaltime()
orgmtime()
functions. RaiseOSError
instead ofValueError
onlocaltime()
orgmtime()
failure.
-
classmethod
datetime.
utcfromtimestamp
(timestamp)¶ Return the UTC
datetime
corresponding to the POSIX timestamp, withtzinfo
None
. This may raiseOverflowError
, if the timestamp is out of the range of values supported by the platform Cgmtime()
function, andOSError
ongmtime()
failure. It’s common for this to be restricted to years in 1970 through 2038.To get an aware
datetime
object, callfromtimestamp()
:datetime.fromtimestamp(timestamp, timezone.utc)
On the POSIX compliant platforms, it is equivalent to the following expression:
datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)
except the latter formula always supports the full years range: between
MINYEAR
andMAXYEAR
inclusive.Distinto en la versión 3.3: Raise
OverflowError
instead ofValueError
if the timestamp is out of the range of values supported by the platform Cgmtime()
function. RaiseOSError
instead ofValueError
ongmtime()
failure.
-
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 unless1 <= ordinal <= datetime.max.toordinal()
. The hour, minute, second and microsecond of the result are all 0, andtzinfo
isNone
.
-
classmethod
datetime.
combine
(date, time)¶ Return a new
datetime
object whose date components are equal to the givendate
object’s, and whose time components andtzinfo
attributes are equal to the giventime
object’s. For anydatetime
object d,d == datetime.combine(d.date(), d.timetz())
. If date is adatetime
object, its time components andtzinfo
attributes are ignored.
-
classmethod
datetime.
strptime
(date_string, format)¶ Return a
datetime
corresponding to date_string, parsed according to format. This is equivalent todatetime(*(time.strptime(date_string, format)[0:6]))
.ValueError
is raised if the date_string and format can’t be parsed bytime.strptime()
or if it returns a value which isn’t a time tuple. For a complete list of formatting directives, see strftime() and strptime() Behavior.
Class attributes:
-
datetime.
max
¶ The latest representable
datetime
,datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999, tzinfo=None)
.
-
datetime.
resolution
¶ The smallest possible difference between non-equal
datetime
objects,timedelta(microseconds=1)
.
Instance attributes (read-only):
-
datetime.
month
¶ Between 1 and 12 inclusive.
-
datetime.
day
¶ Between 1 and the number of days in the given month of the given year.
-
datetime.
hour
¶ In
range(24)
.
-
datetime.
minute
¶ In
range(60)
.
-
datetime.
second
¶ In
range(60)
.
-
datetime.
microsecond
¶ In
range(1000000)
.
-
datetime.
tzinfo
¶ The object passed as the tzinfo argument to the
datetime
constructor, orNone
if none was passed.
Supported operations:
Operation | Result |
---|---|
datetime2 = datetime1 + timedelta |
(1) |
datetime2 = datetime1 - timedelta |
(2) |
timedelta = datetime1 - datetime2 |
(3) |
datetime1 < datetime2 |
Compares datetime to
datetime . (4) |
datetime2 is a duration of timedelta removed from datetime1, moving forward in time if
timedelta.days
> 0, or backward iftimedelta.days
< 0. The result has the sametzinfo
attribute as the input datetime, and datetime2 - datetime1 == timedelta after.OverflowError
is raised if datetime2.year would be smaller thanMINYEAR
or larger thanMAXYEAR
. Note that no time zone adjustments are done even if the input is an aware object.Computes the datetime2 such that datetime2 + timedelta == datetime1. As for addition, the result has the same
tzinfo
attribute as the input datetime, and no time zone adjustments are done even if the input is aware. This isn’t quite equivalent to datetime1 + (-timedelta), because -timedelta in isolation can overflow in cases where datetime1 - timedelta does not.Subtraction of a
datetime
from adatetime
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, thetzinfo
attributes are ignored, and the result is atimedelta
object t such thatdatetime2 + 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.datetime1 is considered less than datetime2 when datetime1 precedes datetime2 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 commontzinfo
attribute is ignored and the base datetimes are compared. If both comparands are aware and have differenttzinfo
attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained fromself.utcoffset()
).Distinto en la versión 3.3: Equality comparisons between naive and aware
datetime
instances don’t raiseTypeError
.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 adatetime
object. However,NotImplemented
is returned instead if the other comparand has atimetuple()
attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when adatetime
object is compared to an object of a different type,TypeError
is raised unless the comparison is==
or!=
. The latter cases returnFalse
orTrue
, respectively.
datetime
objects can be used as dictionary keys. In Boolean contexts,
all datetime
objects are considered to be true.
Instance methods:
-
datetime.
time
()¶ Return
time
object with same hour, minute, second and microsecond.tzinfo
isNone
. See also methodtimetz()
.
-
datetime.
timetz
()¶ Return
time
object with same hour, minute, second, microsecond, and tzinfo attributes. See also methodtime()
.
-
datetime.
replace
([year[, month[, day[, hour[, minute[, second[, microsecond[, tzinfo]]]]]]]])¶ 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.
-
datetime.
astimezone
(tz=None)¶ Return a
datetime
object with newtzinfo
attribute tz, adjusting the date and time data so the result is the same UTC time as self, but in tz’s local time.If provided, tz must be an instance of a
tzinfo
subclass, and itsutcoffset()
anddst()
methods must not returnNone
. self must be aware (self.tzinfo
must not beNone
, andself.utcoffset()
must not returnNone
).If called without arguments (or with
tz=None
) the system local timezone is assumed. The.tzinfo
attribute of the converted datetime instance will be set to an instance oftimezone
with the zone name and offset obtained from the OS.If
self.tzinfo
is tz,self.astimezone(tz)
is equal to self: no adjustment of date or time data is performed. Else the result is local time in time zone tz, representing the same UTC time as self: afterastz = dt.astimezone(tz)
,astz - astz.utcoffset()
will usually have the same date and time data asdt - dt.utcoffset()
. The discussion of classtzinfo
explains the cases at Daylight Saving Time transition boundaries where this cannot be achieved (an issue only if tz models both standard and daylight time).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, usedt.replace(tzinfo=None)
.Note that the default
tzinfo.fromutc()
method can be overridden in atzinfo
subclass to affect the result returned byastimezone()
. Ignoring error cases,astimezone()
acts like: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)
Distinto en la versión 3.3: tz now can be omitted.
-
datetime.
utcoffset
()¶ If
tzinfo
isNone
, returnsNone
, else returnsself.tzinfo.utcoffset(self)
, and raises an exception if the latter doesn’t returnNone
, or atimedelta
object representing a whole number of minutes with magnitude less than one day.
-
datetime.
dst
()¶ If
tzinfo
isNone
, returnsNone
, else returnsself.tzinfo.dst(self)
, and raises an exception if the latter doesn’t returnNone
, or atimedelta
object representing a whole number of minutes with magnitude less than one day.
-
datetime.
tzname
()¶ If
tzinfo
isNone
, returnsNone
, else returnsself.tzinfo.tzname(self)
, raises an exception if the latter doesn’t returnNone
or a string object,
-
datetime.
timetuple
()¶ Return a
time.struct_time
such as returned bytime.localtime()
.d.timetuple()
is equivalent totime.struct_time((d.year, d.month, d.day, d.hour, d.minute, d.second, d.weekday(), yday, dst))
, whereyday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1
is the day number within the current year starting with1
for January 1st. Thetm_isdst
flag of the result is set according to thedst()
method:tzinfo
isNone
ordst()
returnsNone
,tm_isdst
is set to-1
; else ifdst()
returns a non-zero value,tm_isdst
is set to1
; elsetm_isdst
is set to0
.
-
datetime.
utctimetuple
()¶ If
datetime
instance d is naive, this is the same asd.timetuple()
except thattm_isdst
is forced to 0 regardless of whatd.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 atime.struct_time
for the normalized time is returned.tm_isdst
is forced to 0. Note that anOverflowError
may be raised if d.year wasMINYEAR
orMAXYEAR
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 afloat
similar to that returned bytime.time()
.Naive
datetime
instances are assumed to represent local time and this method relies on the platform Cmktime()
function to perform the conversion. Sincedatetime
supports wider range of values thanmktime()
on many platforms, this method may raiseOverflowError
for times far in the past or far in the future.For aware
datetime
instances, the return value is computed as:(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()
Nuevo en la versión 3.3.
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 supplyingtzinfo=timezone.utc
:timestamp = dt.replace(tzinfo=timezone.utc).timestamp()
or by calculating the timestamp directly:
timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)
-
datetime.
weekday
()¶ Return the day of the week as an integer, where Monday is 0 and Sunday is 6. The same as
self.date().weekday()
. See alsoisoweekday()
.
-
datetime.
isoweekday
()¶ Return the day of the week as an integer, where Monday is 1 and Sunday is 7. The same as
self.date().isoweekday()
. See alsoweekday()
,isocalendar()
.
-
datetime.
isocalendar
()¶ Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The same as
self.date().isocalendar()
.
-
datetime.
isoformat
(sep='T')¶ 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:SSIf
utcoffset()
does not returnNone
, a 6-character string is appended, giving the UTC offset in (signed) hours and minutes: YYYY-MM-DDTHH:MM:SS.mmmmmm+HH:MM or, ifmicrosecond
is 0 YYYY-MM-DDTHH:MM:SS+HH:MMThe 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'
-
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 totime.ctime(time.mktime(d.timetuple()))
on platforms where the native Cctime()
function (whichtime.ctime()
invokes, but whichdatetime.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 strftime() and strptime() Behavior.
-
datetime.
__format__
(format)¶ Same as
datetime.strftime()
. This makes it possible to specify a format string for adatetime
object when usingstr.format()
. For a complete list of formatting directives, see strftime() and strptime() Behavior.
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 # doctest: +ELLIPSIS
datetime.datetime(2006, 6, 14, 14, 0, tzinfo=<GMT2 object at 0x...>)
>>> dt2 # doctest: +ELLIPSIS
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>)
>>> dt2.utctimetuple() == dt3.utctimetuple()
True
8.1.5. time
Objects¶
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)¶ All arguments are optional. tzinfo may be
None
, or an instance of atzinfo
subclass. The remaining arguments may be integers, in the following ranges:0 <= hour < 24
0 <= minute < 60
0 <= second < 60
0 <= microsecond < 1000000
.
If an argument outside those ranges is given,
ValueError
is raised. All default to0
except tzinfo, which defaults toNone
.
Class attributes:
-
time.
resolution
¶ The smallest possible difference between non-equal
time
objects,timedelta(microseconds=1)
, although note that arithmetic ontime
objects is not supported.
Instance attributes (read-only):
-
time.
hour
¶ In
range(24)
.
-
time.
minute
¶ In
range(60)
.
-
time.
second
¶ In
range(60)
.
-
time.
microsecond
¶ In
range(1000000)
.
-
time.
tzinfo
¶ The object passed as the tzinfo argument to the
time
constructor, orNone
if none was passed.
Supported operations:
comparison of
time
totime
, 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 commontzinfo
attribute is ignored and the base times are compared. If both comparands are aware and have differenttzinfo
attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained fromself.utcoffset()
). In order to stop mixed-type comparisons from falling back to the default comparison by object address, when atime
object is compared to an object of a different type,TypeError
is raised unless the comparison is==
or!=
. The latter cases returnFalse
orTrue
, respectively.hash, use as dict key
efficient pickling
In boolean contexts, a time
object is always considered to be true.
Distinto en la versión 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.
Instance methods:
-
time.
replace
([hour[, minute[, second[, microsecond[, tzinfo]]]]])¶ Return a
time
with the same value, except for those attributes given new values by whichever keyword arguments are specified. Note thattzinfo=None
can be specified to create a naivetime
from an awaretime
, without conversion of the time data.
-
time.
isoformat
()¶ Return a string representing the time in ISO 8601 format, HH:MM:SS.mmmmmm or, if self.microsecond is 0, HH:MM:SS If
utcoffset()
does not returnNone
, 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
-
time.
__str__
()¶ For a time t,
str(t)
is equivalent tot.isoformat()
.
-
time.
strftime
(format)¶ Return a string representing the time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() and strptime() Behavior.
-
time.
__format__
(format)¶ Same as
time.strftime()
. This makes it possible to specify a format string for atime
object when usingstr.format()
. For a complete list of formatting directives, see strftime() and strptime() Behavior.
-
time.
utcoffset
()¶ If
tzinfo
isNone
, returnsNone
, else returnsself.tzinfo.utcoffset(None)
, and raises an exception if the latter doesn’t returnNone
or atimedelta
object representing a whole number of minutes with magnitude less than one day.
-
time.
dst
()¶ If
tzinfo
isNone
, returnsNone
, else returnsself.tzinfo.dst(None)
, and raises an exception if the latter doesn’t returnNone
, or atimedelta
object representing a whole number of minutes with magnitude less than one day.
-
time.
tzname
()¶ If
tzinfo
isNone
, returnsNone
, else returnsself.tzinfo.tzname(None)
, or raises an exception if the latter doesn’t returnNone
or a string object.
Example:
>>> 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 # doctest: +ELLIPSIS
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. tzinfo
Objects¶
-
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 thedatetime
methods you use. Thedatetime
module supplies a simple concrete subclass oftzinfo
,timezone
, which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT.An instance of (a concrete subclass of)
tzinfo
can be passed to the constructors fordatetime
andtime
objects. The latter objects view their attributes as being in local time, and thetzinfo
object supports methods revealing offset of local time from UTC, the name of the time zone, and DST offset, all relative to a date or time object passed to them.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 awaredatetime
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, returnNone
. Else the value returned must be atimedelta
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 ofutcoffset()
will probably look like one of these two:return CONSTANT # fixed-offset class return CONSTANT + self.dst(dt) # daylight-aware class
If
utcoffset()
does not returnNone
,dst()
should not returnNone
either.The default implementation of
utcoffset()
raisesNotImplementedError
.
-
tzinfo.
dst
(dt)¶ Return the daylight saving time (DST) adjustment, in minutes east of UTC, or
None
if DST information isn’t known. Returntimedelta(0)
if DST is not in effect. If DST is in effect, return the offset as atimedelta
object (seeutcoffset()
for details). Note that DST offset, if applicable, has already been added to the UTC offset returned byutcoffset()
, so there’s no need to consultdst()
unless you’re interested in obtaining DST info separately. For example,datetime.timetuple()
calls itstzinfo
attribute’sdst()
method to determine how thetm_isdst
flag should be set, andtzinfo.fromutc()
callsdst()
to account for DST changes when crossing time zones.An instance tz of a
tzinfo
subclass that models both standard and daylight times must be consistent in this sense:tz.utcoffset(dt) - tz.dst(dt)
must return the same result for every
datetime
dt withdt.tzinfo == tz
For sanetzinfo
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 ofdatetime.astimezone()
relies on this, but cannot detect violations; it’s the programmer’s responsibility to ensure it. If atzinfo
subclass cannot guarantee this, it may be able to override the default implementation oftzinfo.fromutc()
to work correctly withastimezone()
regardless.Most implementations of
dst()
will probably look like one of these two:def dst(self, dt): # a fixed-offset class: doesn't account for DST return timedelta(0)
or
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)
The default implementation of
dst()
raisesNotImplementedError
.
-
tzinfo.
tzname
(dt)¶ Return the time zone name corresponding to the
datetime
object dt, as a string. Nothing about string names is defined by thedatetime
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. ReturnNone
if a string name isn’t known. Note that this is a method rather than a fixed string primarily because sometzinfo
subclasses will wish to return different names depending on the specific value of dt passed, especially if thetzinfo
class is accounting for daylight time.The default implementation of
tzname()
raisesNotImplementedError
.
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.
There is one more tzinfo
method that a subclass may wish to override:
-
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 offromutc()
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 defaultfromutc()
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 defaultfromutc()
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 ofastimezone()
andfromutc()
may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes.Skipping code for error cases, the default
fromutc()
implementation acts like: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
ZERO = timedelta(0)
HOUR = timedelta(hours=1)
# A UTC class.
class UTC(tzinfo):
"""UTC"""
def utcoffset(self, dt):
return ZERO
def tzname(self, dt):
return "UTC"
def dst(self, dt):
return ZERO
utc = UTC()
# A class building tzinfo objects for fixed-offset time zones.
# Note that FixedOffset(0, "UTC") is a different way to build a
# UTC tzinfo object.
class FixedOffset(tzinfo):
"""Fixed offset in minutes east from UTC."""
def __init__(self, offset, name):
self.__offset = timedelta(minutes=offset)
self.__name = name
def utcoffset(self, dt):
return self.__offset
def tzname(self, dt):
return self.__name
def dst(self, dt):
return ZERO
# A class capturing the platform's idea of local time.
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 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; 1am standard time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 1)
# 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; 1am standard 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, 1)
# 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;
# 1am standard 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
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
# Find start and end times for US DST. For years before 1967, return
# ZERO for no DST.
if 2006 < dt.year:
dststart, dstend = DSTSTART_2007, DSTEND_2007
elif 1986 < dt.year < 2007:
dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
elif 1966 < dt.year < 1987:
dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
else:
return ZERO
start = first_sunday_on_or_after(dststart.replace(year=dt.year))
end = first_sunday_on_or_after(dstend.replace(year=dt.year))
# Can't compare naive to aware objects, so strip the timezone from
# dt first.
if start <= dt.replace(tzinfo=None) < end:
return HOUR
else:
return ZERO
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. In order for astimezone()
to make this guarantee, the
tzinfo.dst()
method must consider times in the «missing hour» (2:MM for
Eastern) to be in daylight time.
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. In order for
astimezone()
to make this guarantee, the tzinfo.dst()
method must
consider times in the «repeated hour» to be in standard time. This is easily
arranged, as in the example, by expressing DST switch times in the time zone’s
standard local time.
Applications that can’t bear such ambiguities should avoid using hybrid
tzinfo
subclasses; there are no ambiguities when using timezone
,
or any other fixed-offset tzinfo
subclass (such as a class representing
only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
Ver también
- pytz
The standard library has
timezone
class for handling arbitrary fixed offsets from UTC andtimezone.utc
as UTC timezone instance.pytz library brings the IANA timezone database (also known as the Olson database) to Python and its usage is recommended.
- IANA timezone database
- The Time Zone Database (often called tz or zoneinfo) contains code and data that represent the history of local time for many representative locations around the globe. It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules.
8.1.7. timezone
Objects¶
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])¶ 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)
andtimedelta(hours=24)
and represent a whole number of minutes, otherwiseValueError
is raised.The name argument is optional. If specified it must be a string that is used as the value returned by the
tzname(dt)
method. Otherwise,tzname(dt)
returns a string “UTCsHH:MM”, where s is the sign of offset, HH and MM are two digits ofoffset.hours
andoffset.minutes
respectively.Nuevo en la versión 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 atimedelta
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 or a string “UTCsHH:MM”, where s is the sign of offset, HH and MM are two digits ofoffset.hours
andoffset.minutes
respectively.
-
timezone.
dst
(dt)¶ Always returns
None
.
-
timezone.
fromutc
(dt)¶ Return
dt + offset
. The dt argument must be an awaredatetime
instance, withtzinfo
set toself
.
Class attributes:
-
timezone.
utc
¶ The UTC timezone,
timezone(timedelta(0))
.
8.1.8. strftime()
and strptime()
Behavior¶
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]))
.
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.
Directive | Meaning | Example | Notes |
---|---|---|---|
%a |
Weekday as locale’s abbreviated name. | Sun, Mon, …, Sat
(en_US);
So, Mo, …, Sa
(de_DE)
|
(1) |
%A |
Weekday as locale’s full name. | Sunday, Monday, …,
Saturday (en_US);
Sonntag, Montag, …,
Samstag (de_DE)
|
(1) |
%w |
Weekday as a decimal number, where 0 is Sunday and 6 is Saturday. | 0, 1, …, 6 | |
%d |
Day of the month as a zero-padded decimal number. | 01, 02, …, 31 | |
%b |
Month as locale’s abbreviated name. | Jan, Feb, …, Dec
(en_US);
Jan, Feb, …, Dez
(de_DE)
|
(1) |
%B |
Month as locale’s full name. | January, February,
…, December (en_US);
Januar, Februar, …,
Dezember (de_DE)
|
(1) |
%m |
Month as a zero-padded decimal number. | 01, 02, …, 12 | |
%y |
Year without century as a zero-padded decimal number. | 00, 01, …, 99 | |
%Y |
Year with century as a decimal number. | 0001, 0002, …, 2013, 2014, …, 9998, 9999 | (2) |
%H |
Hour (24-hour clock) as a zero-padded decimal number. | 00, 01, …, 23 | |
%I |
Hour (12-hour clock) as a zero-padded decimal number. | 01, 02, …, 12 | |
%p |
Locale’s equivalent of either AM or PM. | AM, PM (en_US);
am, pm (de_DE)
|
(1), (3) |
%M |
Minute as a zero-padded decimal number. | 00, 01, …, 59 | |
%S |
Second as a zero-padded decimal number. | 00, 01, …, 59 | (4) |
%f |
Microsecond as a decimal number, zero-padded on the left. | 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 |
Time zone name (empty string if the object is naive). | (empty), UTC, EST, CST | |
%j |
Day of the year as a zero-padded decimal number. | 001, 002, …, 366 | |
%U |
Week number of the year (Sunday as the first day of the week) as a zero padded decimal number. All days in a new year preceding the first Sunday are considered to be in week 0. | 00, 01, …, 53 | (7) |
%W |
Week number of the year (Monday as the first day of the week) as a decimal number. All days in a new year preceding the first Monday are considered to be in week 0. | 00, 01, …, 53 | (7) |
%c |
Locale’s appropriate date and time representation. | Tue Aug 16 21:30:00
1988 (en_US);
Di 16 Aug 21:30:00
1988 (de_DE)
|
(1) |
%x |
Locale’s appropriate date representation. | 08/16/88 (None);
08/16/1988 (en_US);
16.08.1988 (de_DE)
|
(1) |
%X |
Locale’s appropriate time representation. | 21:30:00 (en_US);
21:30:00 (de_DE)
|
(1) |
%% |
A literal '%' character. |
% |
Notes:
Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, «month/day/year» versus «day/month/year»), and the output may contain Unicode characters encoded using the locale’s default encoding (for example, if the current locale is
ja_JP
, the default encoding could be any one ofeucJP
,SJIS
, orutf-8
; uselocale.getlocale()
to determine the current locale’s encoding).The
strptime()
method can parse years in the full [1, 9999] range, but years < 1000 must be zero-filled to 4-digit width.Distinto en la versión 3.2: In previous versions,
strftime()
method was restricted to years >= 1900.Distinto en la versión 3.3: In version 3.2,
strftime()
method was restricted to years >= 1000.When used with the
strptime()
method, the%p
directive only affects the output hour field if the%I
directive is used to parse the hour.Unlike the
time
module, thedatetime
module does not support leap seconds.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).For a naive object, the
%z
and%Z
format codes are replaced by empty strings.For an aware object:
%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, ifutcoffset()
returnstimedelta(hours=-3, minutes=-30)
,%z
is replaced with the string'-0330'
.%Z
If
tzname()
returnsNone
,%Z
is replaced by an empty string. Otherwise%Z
is replaced by the returned value, which must be a string.
When used with the
strptime()
method,%U
and%W
are only used in calculations when the day of the week and the year are specified.
Footnotes
[1] | If, that is, we ignore the effects of Relativity |