tz

This module offers timezone implementations subclassing the abstract datetime.tzinfo type. There are classes to handle tzfile format files (usually are in /etc/localtime, /usr/share/zoneinfo, etc), TZ environment string (in all known formats), given ranges (with help from relative deltas), local machine timezone, fixed offset timezone, and UTC timezone.

Objects

dateutil.tz.UTC: A convenience instance of dateutil.tz.tzutc.

Added in version 2.7.0.

Functions

dateutil.tz.gettz(name=None)

Retrieve a time zone object from a string representation

This function is intended to retrieve the tzinfo subclass that best represents the time zone that would be used if a POSIX TZ variable were set to the same value.

If no argument or an empty string is passed to gettz, local time is returned:

>>> gettz()
tzfile('/etc/localtime')

This function is also the preferred way to map IANA tz database keys to tzfile objects:

>>> gettz('Pacific/Kiritimati')
tzfile('/usr/share/zoneinfo/Pacific/Kiritimati')

On Windows, the standard is extended to include the Windows-specific zone names provided by the operating system:

>>> gettz('Egypt Standard Time')
tzwin('Egypt Standard Time')

Passing a GNU TZ style string time zone specification returns a tzstr object:

>>> gettz('AEST-10AEDT-11,M10.1.0/2,M4.1.0/3')
tzstr('AEST-10AEDT-11,M10.1.0/2,M4.1.0/3')

Parameters:: name – A time zone name (IANA, or, on Windows, Windows keys), location of a tzfile(5) zoneinfo file or TZ variable style time zone specifier. An empty string, no argument or None is interpreted as local time.
Returns:: Returns an instance of one of dateutil’s tzinfo subclasses.

Changed in version 2.7.0: After version 2.7.0, any two calls to gettz using the same input strings will return the same object:

>>> tz.gettz('America/Chicago') is tz.gettz('America/Chicago')
True

In addition to improving performance, this ensures that “same zone” semantics are used for datetimes in the same zone.

gettz.nocache(): A non-cached version of gettz

gettz.cache_clear()

dateutil.tz.enfold(dt, fold=1)[source]

Provides a unified interface for assigning the fold attribute to datetimes both before and after the implementation of PEP-495.

Parameters:: fold – The value for the fold attribute in the returned datetime. This should be either 0 or 1.
Returns:: Returns an object for which getattr(dt, 'fold', 0) returns fold for all versions of Python. In versions prior to Python 3.6, this is a _DatetimeWithFold object, which is a subclass of datetime.datetime with the fold attribute added, if fold is 1.

Added in version 2.6.0.

dateutil.tz.datetime_ambiguous(dt, tz=None)[source]

Given a datetime and a time zone, determine whether or not a given datetime is ambiguous (i.e if there are two times differentiated only by their DST status).

Parameters:

dt – A datetime.datetime (whose time zone will be ignored if tz is provided.)
tz – A datetime.tzinfo with support for the fold attribute. If None or not provided, the datetime’s own time zone will be used.

Returns:

Returns a boolean value whether or not the “wall time” is ambiguous in tz.

Added in version 2.6.0.

dateutil.tz.datetime_exists(dt, tz=None)[source]

Given a datetime and a time zone, determine whether or not a given datetime would fall in a gap.

Parameters:

dt – A datetime.datetime (whose time zone will be ignored if tz is provided.)
tz – A datetime.tzinfo with support for the fold attribute. If None or not provided, the datetime’s own time zone will be used.

Returns:

Returns a boolean value whether or not the “wall time” exists in tz.

Added in version 2.7.0.

dateutil.tz.resolve_imaginary(dt)[source]

Given a datetime that may be imaginary, return an existing datetime.

This function assumes that an imaginary datetime represents what the wall time would be in a zone had the offset transition not occurred, so it will always fall forward by the transition’s change in offset.

>>> from dateutil import tz
>>> from datetime import datetime
>>> NYC = tz.gettz('America/New_York')
>>> print(tz.resolve_imaginary(datetime(2017, 3, 12, 2, 30, tzinfo=NYC)))
2017-03-12 03:30:00-04:00

>>> KIR = tz.gettz('Pacific/Kiritimati')
>>> print(tz.resolve_imaginary(datetime(1995, 1, 1, 12, 30, tzinfo=KIR)))
1995-01-02 12:30:00+14:00

As a note, datetime.astimezone() is guaranteed to produce a valid, existing datetime, so a round-trip to and from UTC is sufficient to get an extant datetime, however, this generally “falls back” to an earlier time rather than falling forward to the STD side (though no guarantees are made about this behavior).

Parameters:: dt – A datetime.datetime which may or may not exist.
Returns:: Returns an existing datetime.datetime. If dt was not imaginary, the datetime returned is guaranteed to be the same object passed to the function.

Added in version 2.7.0.

Classes

class dateutil.tz.tzutc[source]

This is a tzinfo object that represents the UTC time zone.

Examples:

>>> from datetime import *
>>> from dateutil.tz import *

>>> datetime.now()
datetime.datetime(2003, 9, 27, 9, 40, 1, 521290)

>>> datetime.now(tzutc())
datetime.datetime(2003, 9, 27, 12, 40, 12, 156379, tzinfo=tzutc())

>>> datetime.now(tzutc()).tzname()
'UTC'

Changed in version 2.7.0: tzutc() is now a singleton, so the result of tzutc() will always return the same object.

>>> from dateutil.tz import tzutc, UTC
>>> tzutc() is tzutc()
True
>>> tzutc() is UTC
True

class dateutil.tz.tzoffset(name, offset)[source]

A simple class for representing a fixed offset from UTC.

Parameters:

name – The timezone name, to be returned when tzname() is called.
offset – The time zone offset in seconds, or (since version 2.6.0, represented as a datetime.timedelta object).

class dateutil.tz.tzlocal[source]: A tzinfo subclass built around the time timezone functions.

class dateutil.tz.tzwinlocal[source]

Class representing the local time zone information in the Windows registry

While dateutil.tz.tzlocal makes system calls (via the time module) to retrieve time zone information, tzwinlocal retrieves the rules directly from the Windows registry and creates an object like dateutil.tz.tzwin.

Because Windows does not have an equivalent of time.tzset(), on Windows, dateutil.tz.tzlocal instances will always reflect the time zone settings at the time that the process was started, meaning changes to the machine’s time zone settings during the run of a program on Windows will not be reflected by dateutil.tz.tzlocal. Because tzwinlocal reads the registry directly, it is unaffected by this issue.

Note

Only available on Windows

display(): Return the display name of the time zone.

transitions(year)

For a given year, get the DST on and off transition times, expressed always on the standard time side. For zones with no transitions, this function returns None.

Parameters:: year – The year whose transitions you would like to query.
Returns:: Returns a tuple of datetime.datetime objects, (dston, dstoff) for zones with an annual DST transition, or None for fixed offset zones.

class dateutil.tz.tzrange(stdabbr, stdoffset=None, dstabbr=None, dstoffset=None, start=None, end=None)[source]

The tzrange object is a time zone specified by a set of offsets and abbreviations, equivalent to the way the TZ variable can be specified in POSIX-like systems, but using Python delta objects to specify DST start, end and offsets.

Parameters:

stdabbr – The abbreviation for standard time (e.g. 'EST').
stdoffset –
An integer or datetime.timedelta object or equivalent specifying the base offset from UTC.

If unspecified, +00:00 is used.
dstabbr –
The abbreviation for DST / “Summer” time (e.g. 'EDT').

If specified, with no other DST information, DST is assumed to occur and the default behavior or dstoffset, start and end is used. If unspecified and no other DST information is specified, it is assumed that this zone has no DST.

If this is unspecified and other DST information is is specified, DST occurs in the zone but the time zone abbreviation is left unchanged.
dstoffset – A an integer or datetime.timedelta object or equivalent specifying the UTC offset during DST. If unspecified and any other DST information is specified, it is assumed to be the STD offset +1 hour.
start –
A relativedelta.relativedelta object or equivalent specifying the time and time of year that daylight savings time starts. To specify, for example, that DST starts at 2AM on the 2nd Sunday in March, pass:

relativedelta(hours=2, month=3, day=1, weekday=SU(+2))

If unspecified and any other DST information is specified, the default value is 2 AM on the first Sunday in April.
end – A relativedelta.relativedelta object or equivalent representing the time and time of year that daylight savings time ends, with the same specification method as in start. One note is that this should point to the first time in the standard zone, so if a transition occurs at 2AM in the DST zone and the clocks are set back 1 hour to 1AM, set the hours parameter to +1.

Examples:

>>> tzstr('EST5EDT') == tzrange("EST", -18000, "EDT")
True

>>> from dateutil.relativedelta import *
>>> range1 = tzrange("EST", -18000, "EDT")
>>> range2 = tzrange("EST", -18000, "EDT", -14400,
...                  relativedelta(hours=+2, month=4, day=1,
...                                weekday=SU(+1)),
...                  relativedelta(hours=+1, month=10, day=31,
...                                weekday=SU(-1)))
>>> tzstr('EST5EDT') == range1 == range2
True

class dateutil.tz.tzstr(s, posix_offset=False)[source]

tzstr objects are time zone objects specified by a time-zone string as it would be passed to a TZ variable on POSIX-style systems (see the GNU C Library: TZ Variable for more details).

There is one notable exception, which is that POSIX-style time zones use an inverted offset format, so normally GMT+3 would be parsed as an offset 3 hours behind GMT. The tzstr time zone object will parse this as an offset 3 hours ahead of GMT. If you would like to maintain the POSIX behavior, pass a True value to posix_offset.

The tzrange object provides the same functionality, but is specified using relativedelta.relativedelta objects. rather than strings.

Parameters:

s – A time zone string in TZ variable format. This can be a bytes (2.x: str), str (2.x: unicode) or a stream emitting unicode characters (e.g. StringIO).
posix_offset – Optional. If set to True, interpret strings such as GMT+3 or UTC+3 as being 3 hours behind UTC rather than ahead, per the POSIX standard.

Caution

Prior to version 2.7.0, this function also supported time zones in the format:

EST5EDT,4,0,6,7200,10,0,26,7200,3600

EST5EDT,4,1,0,7200,10,-1,0,7200,3600

This format is non-standard and has been deprecated; this function will raise a DeprecatedTZFormatWarning until support is removed in a future version.

class dateutil.tz.tzical(fileobj)[source]

This object is designed to parse an iCalendar-style VTIMEZONE structure as set out in RFC 5545 Section 4.6.5 into one or more tzinfo objects.

Parameters:: fileobj – A file or stream in iCalendar format, which should be UTF-8 encoded with CRLF endings.

get(tzid=None)[source]

Retrieve a datetime.tzinfo object by its tzid.

Parameters:: tzid – If there is exactly one time zone available, omitting tzid or passing None value returns it. Otherwise a valid key (which can be retrieved from keys()) is required.
Raises:: ValueError – Raised if tzid is not specified but there are either more or fewer than 1 zone defined.
Returns:: Returns either a datetime.tzinfo object representing the relevant time zone or None if the tzid was not found.

keys()[source]: Retrieves the available time zones as a list.

class dateutil.tz.tzwin(name)[source]

Time zone object created from the zone info in the Windows registry

These are similar to dateutil.tz.tzrange objects in that the time zone data is provided in the format of a single offset rule for either 0 or 2 time zone transitions per year.

Param:: name The name of a Windows time zone key, e.g. “Eastern Standard Time”. The full list of keys can be retrieved with tzwin.list().

Note

Only available on Windows

display(): Return the display name of the time zone.

static list(): Return a list of all time zones known to the system.

transitions(year)

For a given year, get the DST on and off transition times, expressed always on the standard time side. For zones with no transitions, this function returns None.

Parameters:: year – The year whose transitions you would like to query.
Returns:: Returns a tuple of datetime.datetime objects, (dston, dstoff) for zones with an annual DST transition, or None for fixed offset zones.