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Data updates

- Updated tzdata version to 2021a. (gh pr 1128)


- Fixed a bug in the parser where non-``ValueError`` exceptions would be raised
during exception handling; this would happen, for example, if an
``IllegalMonthError`` was raised in ``dateutil`` code. Fixed by Mark Bailey.
(gh issue 981, pr 987).
- Fixed the custom ``repr`` for ``dateutil.parser.ParserError``, which was not
defined due to an indentation error. (gh issue 991, gh pr 993)
- Fixed a bug that caused ``b'`` prefixes to appear in parse_isodate exception
messages. Reported and fixed by Paul Brown (pawl) (gh pr 1122)
- Make ``isoparse`` raise when trying to parse times with inconsistent use of
`:` separator. Reported and fixed by mariocj89 (gh pr 1125).
- Fixed ``tz.gettz()`` not returning local time when passed an empty string.
Reported by labrys (gh issues 925, 926). Fixed by ffe4 (gh pr 1024)

Documentation changes

- Rearranged parser documentation into "Functions", "Classes" and "Warnings and
Exceptions" categories. (gh issue 992, pr 994).
- Updated ``parser.parse`` documentation to reflect the switch from
``ValueError`` to ``ParserError``. (gh issue 992, pr 994).
- Fixed methods in the ``rrule`` module not being displayed in the docs. (gh pr
- Changed some relative links in the exercise documentation to refer to the
document locations in the input tree, rather than the generated HTML files in
the HTML output tree (which presumably will not exist in non-HTML output
formats). (gh pr 1078).


- Moved ````, ```` and ```` to
pytest. Reported and fixed by jpurviance (gh pr 978)
- Added project_urls for documentation and source. Patch by andriyor (gh pr
- Simplified handling of bytes and bytearray in ``_parser._timelex``. Reported
and fixed by frenzymadness (gh issue 1060).
- Changed the tests against the upstream tz database to always generate fat
binaries, since until GH-590 and GH-1059 are resolved, "slim" zic binaries
will cause problems in many zones, causing the tests to fail. This also
updates ``zoneinfo.rebuild`` to always generate fat binaries. (gh pr 1076).
- Moved sdist and wheel generation to use `python-build`. Reported and fixed by
mariocj89 (gh pr 1133).



Data updates

- Updated tzdata version to 2019c.


- Fixed a race condition in the ``tzoffset`` and ``tzstr`` "strong" caches on
Python 2.7. Reported by kainjow (gh issue 901).
- Parsing errors will now raise ``ParserError``, a subclass of ``ValueError``,
which has a nicer string representation. Patch by gfyoung (gh pr 881).
- ``parser.parse`` will now raise ``TypeError`` when ``tzinfos`` is passed a
type that cannot be interpreted as a time zone. Prior to this change, it
would raise an ``UnboundLocalError`` instead. Patch by jbrockmendel (gh pr
- Changed error message raised when when passing a ``bytes`` object as the time
zone name to gettz in Python 3. Reported and fixed by labrys () (gh issue
927, gh pr 935).
- Changed compatibility logic to support a potential Python 4.0 release. Patch
by Hugo van Kemenade (gh pr 950).
- Updated many modules to use ``tz.UTC`` in favor of ``tz.tzutc()`` internally,
to avoid an unnecessary function call. (gh pr 910).
- Fixed issue where ```` was using a backported version of
``contextlib.nullcontext`` even in Python 3.7 due to a malformed import
statement. (gh pr 963).


- Switched from using assertWarns to using pytest.warns in the test suite. (gh
pr 969).
- Fix typo in setup.cfg causing PendingDeprecationWarning to not be explicitly
specified as an error in the warnings filter. (gh pr 966)
- Fixed issue where ``test_tzlocal_offset_equal`` would fail in certain
environments (such as FreeBSD) due to an invalid assumption about what time
zone names are provided. Reported and fixed by Kubilay Kocak (gh issue 918,
pr 928).
- Fixed a minor bug in ``test_isoparser`` related to ``bytes``/``str``
handling. Fixed by fhuang5 (gh issue 776, gh pr 879).
- Explicitly listed all markers used in the pytest configuration. (gh pr 915)
- Extensive improvements to the parser test suite, including the adoption of
``pytest``-style tests and the addition of parametrization of several test
cases. Patches by jbrockmendel (gh prs 735, 890, 892, 894).
- Added tests for tzinfos input types. Patch by jbrockmendel (gh pr 891).
- Fixed failure of test suite when changing the TZ variable is forbidden.
Patch by shadchin (gh pr 893).
- Pinned all test dependencies on Python 3.3. (gh prs 934, 962)

Documentation changes

- Fixed many misspellings, typos and styling errors in the comments and
documentation. Patch by Hugo van Kemenade (gh pr 952).


- Added Python 3.8 to the trove classifiers. (gh pr 970)
- Moved as many keys from ```` to ``setup.cfg`` as possible. Fixed by
FakeNameSE, aquinlan82, jachen20, and gurgenz221 (gh issue 871, gh pr
- Reorganized ``parser`` methods by functionality. Patch by jbrockmendel (gh
pr 882).
- Switched ```` over to using ```` for creating releases,
rather than direct invocations of ````. Fixed by smeng10 (gh issue
869, gh pr 875).
- Added a "build" environment into the tox configuration, to handle dependency
management when making releases. Fixed by smeng10 (gh issue 870,r
gh pr 876).
- GH 916, GH 971



Data updates

- Updated tzdata version to to 2018i.


- Added support for ``EXDATE`` parameters when parsing ``rrule`` strings.
Reported by mlorant (gh issue 410), fixed by nicoe (gh pr 859).
- Added support for sub-minute time zone offsets in Python 3.6+.
Fixed by cssherry (gh issue 582, pr 763)
- Switched the ``tzoffset``, ``tzstr`` and ``gettz`` caches over to using weak
references, so that the cache expires when no other references to the
original ``tzinfo`` objects exist. This cache-expiry behavior is not
guaranteed in the public interface and may change in the future. To improve
performance in the case where transient references to the same time zones
are repeatedly created but no strong reference is continuously held, a
smaller "strong value" cache was also added. Weak value cache implemented by
cs-cordero (gh pr 672, 801), strong cache added by
Gökçen Nurlu (gh issue 691, gh pr 761)


- Add support for ISO 8601 times with comma as the decimal separator in the
``dateutil.parser.isoparse`` function. (gh pr 721)
- Changed handling of ``T24:00`` to be compliant with the standard. ``T24:00``
now represents midnight on the *following* day.
Fixed by cheukting (gh issue 658, gh pr 751)
- Fixed an issue where ``isoparser.parse_isotime`` was unable to handle the
``24:00`` variant representation of midnight. (gh pr 773)
- Added support for more than 6 fractional digits in `isoparse`.
Reported and fixed by jayschwa (gh issue 786, gh pr 787).
- Added 'z' (lower case Z) as valid UTC time zone in isoparser.
Reported by cjgibson (gh issue 820). Fixed by Cheukting (gh pr 822)
- Fixed a bug with base offset changes during DST in ``tzfile``, and refactored
the way base offset changes are detected. Originally reported on
Stack Overflow by MartinThoma. (gh issue 812, gh pr 810)
- Fixed error condition in ``tz.gettz`` when a non-ASCII timezone is passed on
Windows in Python 2.7. (gh issue 802, pr 861)
- Improved performance and inspection properties of ``tzname`` methods.
(gh pr 811)
- Removed unnecessary binary_type compatibility shims.
Added by jdufresne (gh pr 817)
- Changed ``python test`` to print an error to ``stderr`` and exit
with 1 instead of 0. Reported and fixed by hroncok (gh pr 814)
- Added a ``pyproject.toml`` file with build requirements and an explicitly
specified build backend. (gh issue 736, gh prs 746, 863)

Documentation changes

- Added documentation for the ``rrule.rrulestr`` function.
Fixed by prdickson (gh issue 623, gh pr 762)
- Add documentation for the ```` module and mocked out certain
Windows-specific modules so that autodoc can still be run on non-Windows
systems. (gh issue 442, pr 715)
- Added changelog to documentation. (gh issue 692, gh pr 707)
- Improved documentation on the use of ``until`` and ``count`` parameters in
``rrule``. Fixed by lucaferocino (gh pr 755).
- Added an example of how to use a custom ``parserinfo`` subclass to parse
non-standard datetime formats in the examples documentation for ``parser``.
Added by prdickson (gh 753)
- Expanded the description and examples in the ``relativedelta`` class.
Contributed by andrewcbennett (gh pr 759)
- Improved the contributing documentation to clarify where to put new changelog
files. Contributed by andrewcbennett (gh pr 757)
- Fixed a broken doctest in the ``relativedelta`` module.
Fixed by nherriot (gh pr 758).
- Reorganized ```` documentation and fixed issue with the
```` docstring. (gh pr 714)


- GH 720, GH 723, GH 726, GH 727, GH 740, GH 750, GH 760, GH 767,
GH 772, GH 773, GH 780, GH 784, GH 785, GH 791, GH 799, GH 813,
GH 836, GH 839, GH 857



Data updates

- Update tzdata to 2018g



Data updates

- Updated tzdata version to 2018f.



Data updates

- Update tzdata to 2018e. (gh pr 710)


- Fixed an issue where ``parser.parse`` would raise ``Decimal``-specific errors
instead of a standard ``ValueError`` if certain malformed values were parsed
(e.g. ``NaN`` or infinite values). Reported and fixed by
amureki (gh issue 662, gh pr 679).
- Fixed issue in ``parser`` where a ``tzinfos`` call explicitly returning
``None`` would throw a ``ValueError``.
Fixed by parsethis (gh issue 661, gh pr 681)
- Fixed incorrect parsing of certain dates earlier than 100 AD when represented
in the form "%B.%Y.%d", e.g. "December.0031.30". (gh issue 687, pr 700)
- Added time zone inference when initializing an ``rrule`` with a specified
``UNTIL`` but without an explicitly specified ``DTSTART``; the time zone
of the generated ``DTSTART`` will now be taken from the ``UNTIL`` rule.
Reported by href (gh issue 652). Fixed by absreim (gh pr 693).

Documentation changes

- Corrected link syntax and updated URL to https for ISO year week number
notation in relativedelta examples. (gh issue 670, pr 711)
- Add doctest examples to tzfile documentation. Done by weatherpattern and
pganssle (gh pr 671)
- Updated the documentation for relativedelta. Removed references to tuple
arguments for weekday, explained effect of weekday(_, 1) and better explained
the order of operations that relativedelta applies. Fixed by kvn219
huangy22 and ElliotJH (gh pr 673)
- Added changelog to documentation. (gh issue 692, gh pr 707)
- Changed order of keywords in rrule docstring. Reported and fixed by
rmahajan14 (gh issue 686, gh pr 695).
- Added documentation for ````. Reported by pganssle (gh
issue 647). Fixed by weatherpattern (gh pr 704)
- Cleaned up malformed RST in the ``tz`` documentation. (gh issue 702, gh pr
- Changed the default theme to ``sphinx_rtd_theme``, and changed the sphinx
configuration accordingly. (gh pr 707)
- Reorganized ```` documentation and fixed issue with the
```` docstring. (gh pr 714)


- GH 674, GH 688, GH 699




- Fixed an issue with the setup script running in non-UTF-8 environment.
Reported and fixed by gergondet (gh pr 651)


- GH 655



Data updates

- Updated tzdata version to 2018d.


- Fixed issue where parser.parse would occasionally raise
decimal.Decimal-specific error types rather than ValueError. Reported by
amureki (gh issue 632). Fixed by pganssle (gh pr 636).
- Improve error message when rrule's dtstart and until are not both naive or
both aware. Reported and fixed by ryanpetrello (gh issue 633, gh pr 634)


- GH 644, GH 648


- Dropped support for Python 2.6 (gh pr 362 by jdufresne)
- Dropped support for Python 3.2 (gh pr 626)
- Updated zoneinfo file to 2018c (gh pr 616)
- Changed licensing scheme so all new contributions are dual licensed under
Apache 2.0 and BSD. (gh pr 542, issue 496)
- Added __all__ variable to the root package. Reported by tebriel
(gh issue 406), fixed by mariocj89 (gh pr 494)
- Added python_requires to so that pip will distribute the right
version of dateutil. Fixed by jakec-github (gh issue 537, pr 552)
- Added the utils submodule, for miscellaneous utilities.
- Added within_delta function to utils - added by justanr (gh issue 432,
gh pr 437)
- Added today function to utils (gh pr 474)
- Added default_tzinfo function to utils (gh pr 475), solving an issue
reported by nealmcb (gh issue 94)
- Added dedicated ISO 8601 parsing function isoparse (gh issue 424).
Initial implementation by pganssle in gh pr 489 and 622, with a
pre-release fix by kirit93 (gh issue 546, gh pr 573).
- Moved parser module into parser/ and officially deprecated the use
of several private functions and classes from that module. (gh pr 501, 515)
- Tweaked parser error message to include rejected string format, added by
pbiering (gh pr 300)
- Add support for parsing bytesarray, reported by uckelman (gh issue 417) and
fixed by uckelman and pganssle (gh pr 514)
- Started raising a warning when the parser finds a timezone string that it
cannot construct a tzinfo instance for (rather than succeeding with no
indication of an error). Reported and fixed by jbrockmendel (gh pr 540)
- Dropped the use of assert in the parser. Fixed by jbrockmendel (gh pr 502)
- Fixed to assertion logic in parser to support dates like '2015-15-May',
reported and fixed by jbrockmendel (gh pr 409)
- Fixed IndexError in parser on dates with trailing colons, reported and fixed
by jbrockmendel (gh pr 420)
- Fixed bug where hours were not validated, leading to improper parse. Reported
by heappro (gh pr 353), fixed by jbrockmendel (gh pr 482)
- Fixed problem parsing strings in %b-%Y-%d format. Reported and fixed by
jbrockmendel (gh pr 481)
- Fixed problem parsing strings in the %d%B%y format. Reported by asishm
(gh issue 360), fixed by jbrockmendel (gh pr 483)
- Fixed problem parsing certain unambiguous strings when year <99 (gh pr 510).
Reported by alexwlchan (gh issue 293).
- Fixed issue with parsing an unambiguous string representation of an ambiguous
datetime such that if possible the correct value for fold is set. Fixes
issue reported by JordonPhillips and pganssle (gh issue 318, 320,
gh pr 517)
- Fixed issue with improper rounding of fractional components. Reported by
dddmello (gh issue 427), fixed by m-dz (gh pr 570)
- Performance improvement to parser from removing certain min() calls. Reported
and fixed by jbrockmendel (gh pr 589)
- Significantly refactored parser code by jbrockmendel (gh prs 419, 436,
490, 498, 539) and pganssle (gh prs 435, 468)
- Implemented of __hash__ for relativedelta and weekday, reported and fixed
by mrigor (gh pr 389)
- Implemented __abs__ for relativedelta. Reported by binnisb and pferreir
(gh issue 350, pr 472)
- Fixed relativedelta.weeks property getter and setter to work for both
negative and positive values. Reported and fixed by souliane (gh issue 459,
pr 460)
- Fixed issue where passing whole number floats to the months or years
arguments of the relativedelta constructor would lead to errors during
addition. Reported by arouanet (gh pr 411), fixed by lkollar (gh pr 553)
- Added a pre-built tz.UTC object representing UTC (gh pr 497)
- Added a cache to tz.gettz so that by default it will return the same object
for identical inputs. This will change the semantics of certain operations
between datetimes constructed with tzinfo=tz.gettz(...). (gh pr 628)
- Changed the behavior of tz.tzutc to return a singleton (gh pr 497, 504)
- Changed the behavior of tz.tzoffset to return the same object when passed the
same inputs, with a corresponding performance improvement (gh pr 504)
- Changed the behavior of tz.tzstr to return the same object when passed the
same inputs. (gh pr 628)
- Added .instance alternate constructors for tz.tzoffset and tz.tzstr, to
allow the construction of a new instance if desired. (gh pr 628)
- Added the tz.gettz.nocache function to allow explicit retrieval of a new
instance of the relevant tzinfo. (gh pr 628)
- Expand definition of tz.tzlocal equality so that the local zone is allow
equality with tzoffset and tzutc. (gh pr 598)
- Deprecated the idiosyncratic tzstr format mentioned in several examples but
evidently designed exclusively for dateutil, and very likely not used by
any current users. (gh issue 595, gh pr 606)
- Added the tz.resolve_imaginary function, which generates a real date from
an imaginary one, if necessary. Implemented by Cheukting (gh issue 339,
gh pr 607)
- Fixed issue where the tz.tzstr constructor would erroneously succeed if
passed an invalid value for tzstr. Fixed by pablogsal (gh issue 259,
gh pr 581)
- Fixed issue with tz.gettz for TZ variables that start with a colon. Reported
and fixed by lapointexavier (gh pr 601)
- Added a lock to tz.tzical's cache. Reported and fixed by Unrud (gh pr 430)
- Fixed an issue with fold support on certain Python 3 implementations that
used the pre-3.6 pure Python implementation of datetime.replace, most
notably pypy3 (gh pr 446).
- Added support for VALUE=DATE-TIME for DTSTART in rrulestr. Reported by potuz
(gh issue 401) and fixed by Unrud (gh pr 429)
- Started enforcing that within VTIMEZONE, the VALUE parameter can only be
omitted or DATE-TIME, per RFC 5545. Reported by Unrud (gh pr 439)
- Added support for TZID parameter for DTSTART in rrulestr. Reported and
fixed by ryanpetrello (gh issue 614, gh pr 624)
- Added 'RRULE:' prefix to rrule strings generated by rrule.__str__, in
compliance with the RFC. Reported by AndrewPashkin (gh issue 86), fixed by
jarondl and mlorant (gh pr 450)
- Switched to setuptools_scm for version management, automatically calculating
a version number from the git metadata. Reported by jreback (gh issue 511),
implemented by Sulley38 (gh pr 564)
- Switched to use find_packages, and started testing against pip
installed versions of dateutil in CI. Fixed issue with parser import
discovered by jreback in pandas-dev/pandas18141. (gh issue 507, pr 509)
- Switched test suite to using pytest (gh pr 495)
- Switched CI over to use tox. Fixed by gaborbernat (gh pr 549)
- Added a test-only dependency on freezegun. (gh pr 474)
- Reduced number of CI builds on Appveyor. Fixed by kirit93 (gh issue 529,
gh pr 579)
- Made xfails strict by default, so that an xpass is a failure. (gh pr 567)
- Added a documentation generation stage to tox and CI. (gh pr 568)
- Added an explicit warning when running python explaining how to run
the test suites with pytest. Fixed by lkollar. (gh issue 544, gh pr 548)
- Added requirements-dev.txt for test dependency management (gh pr 499, 516)
- Fixed code coverage metrics to account for Windows builds (gh pr 526)
- Fixed code coverage metrics to NOT count xfails. Fixed by gaborbernat
(gh issue 519, gh pr 563)
- Style improvement to zoneinfo.tzfile that was confusing to static type
checkers. Reported and fixed by quodlibetor (gh pr 485)
- Several unused imports were removed by jdufresne. (gh pr 486)
- Switched ``isinstance(*, collections.Callable)`` to callable, which is available
on all supported Python versions. Implemented by jdufresne (gh pr 612)
- Added (gh pr 533)
- Added (gh pr 542)
- Corrected metadata to reflect author vs. maintainer, (gh issue 477,
gh pr 538)
- Corrected README to reflect that tests are now run in pytest. Reported and
fixed by m-dz (gh issue 556, gh pr 557)
- Updated all references to RFC 2445 (iCalendar) to point to RFC 5545. Fixed
by mariocj89 (gh issue 543, gh pr 555)
- Corrected parse documentation to reflect proper integer offset units,
reported and fixed by abrugh (gh pr 458)
- Fixed dangling parenthesis in tzoffset documentation (gh pr 461)
- Started including the license file in wheels. Reported and fixed by
jdufresne (gh pr 476)
- Indentation fixes to parser docstring by jbrockmendel (gh pr 492)
- Moved many examples from the "examples" documentation into their appropriate
module documentation pages. Fixed by Tomasz-Kluczkowski and jakec-github
(gh pr 558, 561)
- Fixed documentation so that the parser.isoparse documentation displays.
Fixed by alexchamberlain (gh issue 545, gh pr 560)
- Refactored build and release sections and added setup instructions to
CONTRIBUTING. Reported and fixed by kynan (gh pr 562)
- Cleaned up various dead links in the documentation. (gh pr 602, 608, 618)


- Updated zoneinfo file to 2017b. (gh pr 395)
- Added Python 3.6 to CI testing (gh pr 365)
- Removed duplicate test name that was preventing a test from being run.
Reported and fixed by jdufresne (gh pr 371)
- Fixed testing of folds and gaps, particularly on Windows (gh pr 392)
- Fixed deprecated escape characters in regular expressions. Reported by
nascheme and thierryba (gh issue 361), fixed by thierryba (gh pr 358)
- Many PEP8 style violations and other code smells were fixed by jdufresne
(gh prs 358, 363, 364, 366, 367, 368, 372, 374, 379, 380, 398)
- Improved performance of tzutc and tzoffset objects. (gh pr 391)
- Fixed issue with several time zone classes around DST transitions in any
zones with +0 standard offset (e.g. Europe/London) (gh issue 321, pr 390)
- Fixed issue with fuzzy parsing where tokens similar to AM/PM that are in the
end skipped were dropped in the fuzzy_with_tokens list. Reported and fixed
by jbrockmendel (gh pr 332).
- Fixed issue with parsing dates of the form X m YY. Reported by jbrockmendel.
(gh issue 333, pr 393)
- Added support for parser weekdays with less than 3 characters. Reported by
arcadefoam (gh issue 343), fixed by jonemo (gh pr 382)
- Fixed issue with the addition and subtraction of certain relativedeltas.
Reported and fixed by kootenpv (gh issue 346, pr 347)
- Fixed issue where the COUNT parameter of rrules was ignored if 0. Fixed by
mshenfield (gh pr 330), reported by vaultah (gh issue 329).
- Updated documentation to include the new tz methods. (gh pr 324)
- Update documentation to reflect that the parser can raise TypeError, reported
and fixed by tomchuk (gh issue 336, pr 337)
- Fixed an incorrect year in a parser doctest. Fixed by xlotlu (gh pr 357)
- Moved version information into and set up the versions more


- Added PEP-495-compatible methods to address ambiguous and imaginary dates in
time zones in a backwards-compatible way. Ambiguous dates and times can now
be safely represented by all dateutil time zones. Many thanks to Alexander
Belopolski (abalkin) and Tim Peters tim-one for their inputs on how to
address this. Original issues reported by Yupeng and zed (lP: 1390262,
gh issues 57, 112, 249, 284, 286, prs 127, 225, 248, 264, 302).
- Added new methods for working with ambiguous and imaginary dates to the tz
module. datetime_ambiguous() determines if a datetime is ambiguous for a given
zone and datetime_exists() determines if a datetime exists in a given zone.
This works for all fold-aware datetimes, not just those provided by dateutil.
(gh issue 253, gh pr 302)
- Fixed an issue where dst() in Portugal in 1996 was returning the wrong value
in tz.tzfile objects. Reported by abalkin (gh issue 128, pr 225)
- Fixed an issue where zoneinfo.ZoneInfoFile errors were not being properly
deep-copied. (gh issue 226, pr 225)
- Refactored tzwin and tzrange as a subclass of a common class, tzrangebase, as
there was substantial overlapping functionality. As part of this change,
tzrange and tzstr now expose a transitions() function, which returns the
DST on and off transitions for a given year. (gh issue 260, pr 302)
- Deprecated zoneinfo.gettz() due to confusion with tz.gettz(), in favor of
get() method of zoneinfo.ZoneInfoFile objects. (gh issue 11, pr 310)
- For non-character, non-stream arguments, parser.parse now raises TypeError
instead of AttributeError. (gh issues 171, 269, pr 247)
- Fixed an issue where tzfile objects were not properly handling dst() and
tzname() when attached to datetime.time objects. Reported by ovacephaloid.
(gh issue 292, pr 309)
- /usr/share/lib/zoneinfo was added to TZPATHS for compatibility with Solaris
systems. Reported by dhduvall (gh issue 276, pr 307)
- tzoffset and tzrange objects now accept either a number of seconds or a
datetime.timedelta() object wherever previously only a number of seconds was
allowed. (gh pr 264, 277)
- datetime.timedelta objects can now be added to relativedelta objects. Reported
and added by Alec Nikolas Reiter (justanr) (gh issue 282, pr 283
- Refactored relativedelta.weekday and rrule.weekday into a common base class
to reduce code duplication. (gh issue 140, pr 311)
- An issue where the WKST parameter was improperly rendering in str(rrule) was
reported and fixed by Daniel LePage (dplepage). (gh issue 262, pr 263)
- A replace() method has been added to rrule objects by jendas1, which creates
new rrule with modified attributes, analogous to datetime.replace (gh pr 167)
- Made some significant performance improvements to rrule objects in Python 2.x
(gh pr 245)
- All classes defining equality functions now return NotImplemented when
compared to unsupported classes, rather than raising TypeError, to allow other
classes to provide fallback support. (gh pr 236)
- Several classes have been marked as explicitly unhashable to maintain
identical behavior between Python 2 and 3. Submitted by Roy Williams
(rowillia) (gh pr 296)
- Trailing whitespace in has been removed. Submitted by OmgImAlexis
(gh pr 299)
- Windows-only batch files in build scripts had line endings switched to CRLF.
(gh pr 237)
- adamchainz updated the documentation links to reflect that the canonical
location for readthedocs links is now at .io, not .org. (gh pr 272)
- Made some changes to the CI and codecov to test against newer versions of
Python and pypy, and to adjust the code coverage requirements. For the moment,
full pypy3 compatibility is not supported until a new release is available,
due to upstream bugs in the old version affecting PEP-495 support.
(gh prs 265, 266, 304, 308)
- The full PGP signing key fingerprint was added to the in favor of
the previously used long-id. Reported by valholl (gh issue 287, pr 304)
- Updated zoneinfo to 2016i. (gh issue 298, gh pr 306)


- Updated zoneinfo to 2016d
- Fixed parser bug where unambiguous datetimes fail to parse when dayfirst is
set to true. (gh issue 233, pr 234)
- Bug in zoneinfo file on platforms such as Google App Engine which do not
do not allow importing of subprocess.check_call was reported and fixed by
savraj (gh issue 239, gh pr 240)
- Fixed incorrect version in documentation (gh issue 235, pr 243)


- Updated zoneinfo to 2016c
- Fixed parser bug where yearfirst and dayfirst parameters were not being
respected when no separator was present. (gh issue 81 and 217, pr 229)


- Updated zoneinfo to 2016b
- Changed to explicitly include test suite in source distributions,
with help from koobs (gh issue 193, pr 194, 201, 221)
- Explicitly set all line-endings to LF, except for the NEWS file, on a
per-repository basis (gh pr 218)
- Fixed an issue with improper caching behavior in rruleset objects (gh issue
104, pr 207)
- Changed to an explicit error when rrulestr strings contain a missing BYDAY
(gh issue 162, pr 211)
- tzfile now correctly handles files containing leapcnt (although the leapcnt
information is not actually used). Contributed by hjoukl (gh issue 146, pr
- Fixed recursive import issue with tz module (gh pr 204)
- Added compatibility between tzwin objects and datetime.time objects (gh issue
216, gh pr 219)
- Refactored monolithic test suite by module (gh issue 61, pr 200 and 206)
- Improved test coverage in the relativedelta module (gh pr 215)
- Adjusted documentation to reflect possibly counter-intuitive properties of
RFC-5545-compliant rrules, and other documentation improvements in the rrule
module (gh issue 105, gh issue 149 - pointer to the solution by phep,
pr 213).


- Updated zoneinfo to 2016a
- zoneinfo_metadata file version increased to 2.0 - the updated
script will work with older zoneinfo_metadata.json files, but new metadata
files will not work with older versions. Additionally, we have
started hosting our own mirror of the Olson databases on a GitHub pages
site ( (gh pr #183)
- dateutil zoneinfo tarballs now contain the full zoneinfo_metadata file used
to generate them. (gh issue 27, gh pr 85)
- relativedelta can now be safely subclassed without derived objects reverting
to base relativedelta objects as a result of arithmetic operations.
(lp:1010199, gh issue 44, pr 49)
- relativedelta 'weeks' parameter can now be set and retrieved as a property of
relativedelta instances. (lp: 727525, gh issue 45, pr 49)
- relativedelta now explicitly supports fractional relative weeks, days, hours,
minutes and seconds. Fractional values in absolute parameters (year, day, etc)
are now deprecated. (gh issue 40, pr 190)
- relativedelta objects previously did not use microseconds to determine of two
relativedelta objects were equal. This oversight has been corrected.
Contributed by elprans (gh pr 113)
- rrule now has an xafter() method for retrieving multiple recurrences after a
specified date. (gh pr 38)
- str(rrule) now returns an RFC2445-compliant rrule string, contributed by
schinckel and armicron (lp:1406305, gh issue 47, prs 50, 62 and 160)
- rrule performance under certain conditions has been significantly improved
thanks to a patch contributed by dekoza, based on an article by Brian Beck
(exogen) (gh pr 136)
- The use of both the 'until' and 'count' parameters is now deprecated as
inconsistent with RFC2445 (gh pr 62, 185)
- Parsing an empty string will now raise a ValueError, rather than returning the
datetime passed to the 'default' parameter. (gh issue 78, pr 187)
- tzwinlocal objects now have a meaningful repr() and str() implementation
(gh issue 148, prs 184 and 186)
- Added equality logic for tzwin and tzwinlocal objects. (gh issue 151,
pr 180, 184)
- Added some flexibility in subclassing timelex, and switched the default
behavior over to using string methods rather than comparing against a fixed
list. (gh pr 122, 139)
- An issue causing tzstr() to crash on Python 2.x was fixed. (lp: 1331576,
gh issue 51, pr 55)
- An issue with string encoding causing exceptions under certain circumstances
when tzname() is called was fixed. (gh issue 60, 74, pr 75)
- Parser issue where calling parse() on dates with no day specified when the
day of the month in the default datetime (which is "today" if unspecified) is
greater than the number of days in the parsed month was fixed (this issue
tended to crop up between the 29th and 31st of the month, for obvious reasons)
(canonical gh issue 25, pr 30, 191)
- Fixed parser issue causing fuzzy_with_tokens to raise an unexpected exception
in certain circumstances. Contributed by MichaelAquilina (gh pr 91)
- Fixed parser issue where years > 100 AD were incorrectly parsed. Contributed
by Bachmann1234 (gh pr 130)
- Fixed parser issue where commas were not a valid separator between seconds
and microseconds, preventing parsing of ISO 8601 dates. Contributed by
ryanss (gh issue 28, pr 106)
- Fixed issue with tzwin encoding in locales with non-Latin alphabets
(gh issue 92, pr 98)
- Fixed an issue where tzwin was not being properly imported on Windows.
Contributed by labrys. (gh pr 134)
- Fixed a problem causing issues importing zoneinfo in certain circumstances.
Issue and solution contributed by alexxv (gh issue 97, pr 99)
- Fixed an issue where dateutil timezones were not compatible with basic time
objects. One of many, many timezone related issues contributed and tested by
labrys. (gh issue 132, pr 181)
- Fixed issue where tzwinlocal had an invalid utcoffset. (gh issue 135,
pr 141, 142)
- Fixed issue with tzwin and tzwinlocal where DST transitions were incorrectly
parsed from the registry. (gh issue 143, pr 178)
- no longer suppresses certain OSErrors. Contributed by bjamesv
(gh pr 164)
- An issue that arose when timezone locale changes during runtime has been
fixed by carlosxl and mjschultz (gh issue 100, prs 107, 109)
- Python 3.5 was added to the supported platforms in the metadata (tacaswell
gh pr 159) and the test suites (moreati gh pr 117).
- An issue with tox failing without unittest2 installed in Python 2.6 was fixed
by moreati (gh pr 115)
- Several deprecated functions were replaced in the tests by moreati
(gh pr 116)
- Improved the logic in Travis and Appveyor to alleviate issues where builds
were failing due to connection issues when downloading the IANA timezone
files. In addition to adding our own mirror for the files (gh pr 183), the
download is now retried a number of times (with a delay) (gh pr 177)
- Many failing doctests were fixed by moreati. (gh pr 120)
- Many fixes to the documentation (gh pr 103, gh pr 87 from radarhere,
gh pr 154 from gpoesia, gh pr 156 from awsum, gh pr 168 from ja8zyjits)
- Added a code coverage tool to the CI to help improve the library. (gh pr 182)
- We now have a mailing list -, graciously hosted by


- Updated zoneinfo to 2015b.
- Fixed issue with parsing of tzstr on Python 2.7.x; tzstr will now be decoded
if not a unicode type. gh 51 (lp:1331576), gh pr 55.
- Fix a parser issue where AM and PM tokens were showing up in fuzzy date
stamps, triggering inappropriate errors. gh 56 (lp: 1428895), gh pr 63.
- Missing function "setcachesize" removed from zoneinfo __all__ list by ryanss,
fixing an issue with wildcard imports of dateutil.zoneinfo. (gh pr 66).
- (PyPI only) Fix an issue with source distributions not including the test



- Added explicit check for valid hours if AM/PM is specified in parser.
(gh pr 22, issue 21)
- Fix bug in rrule introduced in 2.4.0 where byweekday parameter was not
handled properly. (gh pr 35, issue 34)
- Fix error where parser allowed some invalid dates, overwriting existing hours
with the last 2-digit number in the string. (gh pr 32, issue 31)
- Fix and add test for Python 2.x compatibility with boolean checking of
relativedelta objects. Implemented by nimasmi (gh pr 43) and Cédric Krier
(lp: 1035038)
- Replaced parse() calls with explicit datetime objects in unit tests unrelated
to parser. (gh pr 36)
- Changed private _byxxx from sets to sorted tuples and fixed one currently
unreachable bug in _construct_byset. (gh pr 54)
- Additional documentation for parser (gh pr 29, 33, 41) and rrule.
- Formatting fixes to documentation of rrule and README.rst.
- Updated zoneinfo to 2015a.



- Fix an issue with relativedelta and freezegun (lp:1374022)
- Fix tzinfo in windows for timezones without dst (lp:1010050, gh 2)
- Ignore missing timezones in windows like in POSIX
- Fix minimal version requirement for six (gh 6)
- Many rrule changes and fixes by pganssle (gh pull requests 13 14 17),
including defusing some infinite loops (gh 4)



- Cleanup directory structure, moved to dateutil/tests/

- Changed many aspects of dealing with the zone info file. Instead of a cache,
all the zones are loaded to memory, but symbolic links are loaded only once,
so not much memory is used.

- The package is now zip-safe, and universal-wheelable, thanks to changes in
the handling of the zoneinfo file.

- Fixed tzwin silently not imported on windows python2

- New maintainer, together with new hosting: GitHub, Travis, Read-The-Docs



- Updated zoneinfo to 2013h

- fuzzy_with_tokens parse addon from Christopher Corley

- Bug with LANG=C fixed by Mike Gilbert



- New maintainer

- Dateutil now works on Python 2.6, 2.7 and 3.2 from same codebase (with six)

- 704047: Ismael Carnales' patch for a new time format

- Small bug fixes, thanks for reporters!



- Ported to Python 3, by Brian Jones. If you need dateutil for Python 2.X,
please continue using the 1.X series.

- There's no such thing as a "PSF License". This source code is now
made available under the Simplified BSD license. See LICENSE for



- As reported by Mathieu Bridon, rrules were matching the bysecond rules
incorrectly against byminute in some circumstances when the SECONDLY
frequency was in use, due to a copy & paste bug. The problem has been
unittested and corrected.

- Adam Ryan reported a problem in the relativedelta implementation which
affected the yearday parameter in the month of January specifically.
This has been unittested and fixed.

- Updated timezone information.



- Updated timezone information.



- Fixed another parser precision problem on conversion of decimal seconds
to microseconds, as reported by Erik Brown. Now these issues are gone
for real since it's not using floating point arithmetic anymore.

- Fixed case where tzrange.utcoffset and tzrange.dst() might fail due
to a date being used where a datetime was expected (reported and fixed
by Lennart Regebro).

- Prevent tzstr from introducing daylight timings in strings that didn't
specify them (reported by Lennart Regebro).

- Calls like gettz("GMT+3") and gettz("UTC-2") will now return the
expected values, instead of the TZ variable behavior.

- Fixed DST signal handling in zoneinfo files. Reported by
Nicholas F. Fabry and John-Mark Gurney.



- Fixed precision problem on conversion of decimal seconds to
microseconds, as reported by Skip Montanaro.

- Fixed bug in constructor of parser, and converted parser classes to
new-style classes. Original report and patch by Michael Elsdörfer.

- Initialize tzid and comps in, to prevent the code from ever
raising a NameError (even with broken files). Johan Dahlin suggested
the fix after a pyflakes run.

- Version is now published in dateutil.__version__, as requested
by Darren Dale.

- All code is compatible with new-style division.



- Now tzfile will round timezones to full-minutes if necessary,
since Python's datetime doesn't support sub-minute offsets.
Thanks to Ilpo Nyyssönen for reporting the issue.

- Removed bare string exceptions, as reported and fixed by
Wilfredo Sánchez Vega.

- Fix bug in leap count parsing (reported and fixed by Eugene Oden).



- Fixed rrule byyearday handling. Abramo Bagnara pointed out that
RFC2445 allows negative numbers.

- Fixed --prefix handling in (by Sidnei da Silva).

- Now tz.gettz() returns a tzlocal instance when not given any
arguments and no other timezone information is found.

- Updating timezone information to version 2005q.



- Fixed parsing of XXhXXm formatted time after day/month/year
has been parsed.

- Added patch by Jeffrey Harris optimizing rrule.__contains__.



- Fixed pickling of timezone types, as reported by
Andreas Köhler.

- Implemented internal timezone information with binary
timezone files. function will now
try to use the system timezone files, and fallback to
the internal versions. It's also possible to ask for
the internal versions directly by using

- New tzwin timezone type, allowing access to Windows
internal timezones (contributed by Jeffrey Harris).

- Fixed parsing of unicode date strings.

- Accept parserinfo instances as the parser constructor
parameter, besides parserinfo (sub)classes.

- Changed weekday to spell the not-set n value as None
instead of 0.

- Fixed other reported bugs.



- Removed ``FREQ_`` prefix from rrule frequency constants
WARNING: this breaks compatibility with previous versions.

- Fixed rrule.between() for cases where "after" is achieved
before even starting, as reported by Andreas Köhler.

- Fixed two digit zero-year parsing (such as 31-Dec-00), as
reported by Jim Abramson, and included test case for this.

- Sort exdate and rdate before iterating over them, so that
it's not necessary to sort them before adding to the rruleset,
as reported by Nicholas Piper.