`datetime` — Basic date and time types¶

The datetime module supplies classes for manipulating dates and times.

While date and time arithmetic is supported, the focus of the implementation is on efficient attribute extraction for output formatting and manipulation.

Tip

Skip to the format codes.

Aware and naive objects¶

Date and time objects may be categorized as “aware” or “naive” depending on whether or not they include time zone information.

With sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, an aware object can locate itself relative to other aware objects. An aware object represents 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 time zone 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.

Only one concrete tzinfo class, the timezone class, is supplied by the datetime module. The timezone class can represent simple time zones with fixed offsets from UTC, such as UTC itself or North American EST and EDT time zones. Supporting time zones 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.

Constants¶

The datetime module exports the following constants:

datetime.MINYEAR¶: The smallest year number allowed in a date or datetime object. MINYEAR is 1.

datetime.MAXYEAR¶: The largest year number allowed in a date or datetime object. MAXYEAR is 9999.

datetime.UTC¶: Alias for the UTC time zone singleton datetime.timezone.utc.

Added in version 3.11.

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, and 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: A combination of a date and a time. Attributes: year, month, day, hour, minute, second, microsecond, and tzinfo.

class datetime.timedelta: A duration expressing the difference between two datetime or date instances to microsecond resolution.

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: A class that implements the tzinfo abstract base class as a fixed offset from the UTC.

Added in version 3.2.

Objects of these types are immutable.

Subclass relationships:

timedelta, tzinfo, time, and date inherit from object; timezone inherits from tzinfo; and datetime inherits from date.

Common properties¶

The date, datetime, time, and timezone types share these common features:

Objects of these types are immutable.
Objects of these types are hashable, meaning that they can be used as dictionary keys.
Objects of these types support efficient pickling via the pickle module.

Determining if an object is aware or naive¶

Objects of the date type are always naive.

An object of type time or datetime may be aware or naive.

A datetime object d is aware if both of the following hold:

d.tzinfo is not None
d.tzinfo.utcoffset(d) does not return None

Otherwise, d is naive.

A time object t is aware if both of the following hold:

t.tzinfo is not None
t.tzinfo.utcoffset(None) does not return None.

Otherwise, t is naive.

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

`timedelta` objects¶

A timedelta object represents a duration, the difference between two datetime or date instances.

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

The following example illustrates how any arguments besides days, seconds and microseconds are “merged” and normalized into those three resulting attributes:

>>> import datetime as dt
>>> delta = dt.timedelta(
...     days=50,
...     seconds=27,
...     microseconds=10,
...     milliseconds=29000,
...     minutes=5,
...     hours=8,
...     weeks=2
... )
>>> # Only days, seconds, and microseconds remain
>>> delta
datetime.timedelta(days=64, seconds=29156, microseconds=10)

Tip

import datetime as dt instead of import datetime or from datetime import datetime to avoid confusion between the module and the class. See How I Import Python’s datetime Module.

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:

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

Since the string representation of timedelta objects can be confusing, use the following recipe to produce a more readable format:

>>> def pretty_timedelta(td):
...     if td.days >= 0:
...         return str(td)
...     return f'-({-td!s})'
...
>>> d = timedelta(hours=-1)
>>> str(d)  # not human-friendly
'-1 day, 23:00:00'
>>> pretty_timedelta(d)
'-(1:00:00)'

Class attributes:

timedelta.min¶: The most negative timedelta object, timedelta(-999999999).

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 is greater than -timedelta.min. -timedelta.max is not representable as a timedelta object.

Instance attributes (read-only):

timedelta.days¶: Between -999,999,999 and 999,999,999 inclusive.

timedelta.seconds¶

Between 0 and 86,399 inclusive.

Caution

It is a somewhat common bug for code to unintentionally use this attribute when it is actually intended to get a total_seconds() value instead:

>>> import datetime as dt
>>> duration = dt.timedelta(seconds=11235813)
>>> duration.days, duration.seconds
(130, 3813)
>>> duration.total_seconds()
11235813.0

timedelta.microseconds¶: Between 0 and 999,999 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)(6)
`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 overall duration `t2` by interval unit `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 representation of the `timedelta` object as a constructor call with canonical attribute values.

Notes:

This is exact but may overflow.
This is exact and cannot overflow.
Division by zero 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(days=-1, seconds=68400)
>>> print(_)
-1 day, 19:00:00
```
The expression t2 - t3 will always be equal to the expression t2 + (-t3) except when t3 is equal to timedelta.max; in that case the former will produce a result while the latter will overflow.

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

Changed in version 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.

timedelta objects support equality and order comparisons.

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). For interval units other than seconds, use the division form directly (for example, td / timedelta(microseconds=1)).

Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy.

Added in version 3.2.

Examples of usage: `timedelta`¶

An additional example of normalization:

>>> # Components of another_year add up to exactly 365 days
>>> import datetime as dt
>>> year = dt.timedelta(days=365)
>>> another_year = dt.timedelta(weeks=40, days=84, hours=23,
...                             minutes=50, seconds=600)
>>> year == another_year
True
>>> year.total_seconds()
31536000.0

Examples of timedelta arithmetic:

>>> import datetime as dt
>>> year = dt.timedelta(days=365)
>>> ten_years = 10 * year
>>> ten_years
datetime.timedelta(days=3650)
>>> ten_years.days // 365
10
>>> nine_years = ten_years - year
>>> nine_years
datetime.timedelta(days=3285)
>>> three_years = nine_years // 3
>>> three_years, three_years.days // 365
(datetime.timedelta(days=1095), 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. [2]

class datetime.date(year, month, day)¶

All arguments are required. Arguments must 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 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().

Changed in version 3.3: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime() function. Raise OSError instead of ValueError on localtime() 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 unless 1 <= ordinal <= date.max.toordinal(). For any date d, date.fromordinal(d.toordinal()) == d.

classmethod date.fromisoformat(date_string)¶

Return a date corresponding to a date_string given in any valid ISO 8601 format, with the following exceptions:

Reduced precision dates are not currently supported (YYYY-MM, YYYY).
Extended date representations are not currently supported (±YYYYYY-MM-DD).
Ordinal dates are not currently supported (YYYY-OOO).

Examples:

>>> import datetime

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datetime — Basic date and time types¶

Aware and naive objects¶

Constants¶

Available types¶

Common properties¶

Determining if an object is aware or naive¶

timedelta objects¶

Examples of usage: timedelta¶

date objects¶

`datetime` — Basic date and time types¶

`timedelta` objects¶

Examples of usage: `timedelta`¶

`date` objects¶