8000 Fix calculating remaining time across DST changes by imrivera · Pull Request #9669 · celery/celery · GitHub

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Fix calculating remaining time across DST changes #9669

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Nusnus merged 1 commit into celery:main from imrivera:fix_calculating_remaining_time_crossing_DST

Apr 17, 2025

+48 −9

Contributor

imrivera commented

•

Description

Fix calculating the remaining time across DST changes.

Python by default uses wall time (not real time) in arithmetic between datetimes with equal non-UTC timezones. For example:

dt1 = datetime(day=10, month=3, year=2019, hour=1, minute=30, tzinfo=ZoneInfo("US/Eastern")  # EST
dt2 = datetime(day=10, month=3, year=2019, hour=3, minute=30, tzinfo=ZoneInfo("US/Eastern")  # EDT
print(f"dt1: {dt1}")
print(f"dt2: {dt2}")
print(f"wall diff: {repr(dt2 - dt1)}")
print(f"real diff: {repr(dt2.astimezone(ZoneInfo("UTC")) - dt1.astimezone(ZoneInfo("UTC")))}")

This will print:

dt1: 2019-03-10 01:30:00-05:00
dt2: 2019-03-10 03:30:00-04:00 
wall diff: datetime.timedelta(seconds=7200)
real diff: datetime.timedelta(seconds=3600)

And in Celery's use case we are interested in the real time, not the wall time.

Interesting blog post about this non-intuitive behavior here

Fixes #9653


          Fix calculating remaining time across DST changes

38141c6

Nusnus self-requested a review

April 17, 2025 13:46

Nusnus reviewed

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Nusnus left a comment

Very nice!
I’ll review it once the CI finishes

codecov bot commented

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.30%. Comparing base (d643c7c) to head (38141c6).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9669   +/-   ##
=======================================
  Coverage   78.30%   78.30%           
=======================================
  Files         153      153           
  Lines       19123    19123           
  Branches     2534     2533    -1     
=======================================
  Hits        14975    14975           
  Misses       3858     3858           
  Partials      290      290

Flag	Coverage Δ
unittests	`78.28% <100.00%> (ø)`

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Nusnus approved these changes

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Nusnus left a comment

LGTM, thank you very much @imrivera !
DST issues are really pesky. Nice fix!

Nusnus merged commit f0c7261 into celery:main

342 of 346 checks passed

github-merge-queue bot pushed a commit to Software-Engineering-Jagiellonian/django-celery-frege that referenced this pull request


          chore(deps): bump celery[redis] from 5.5.1 to 5.5.2 in /backend (#205)

17bdd6b

Bumps [celery[redis]](https://github.com/celery/celery) from 5.5.1 to
5.5.2.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/celery/celery/releases">celery[redis]'s
releases</a>.</em></p>
<blockquote>
<h2>v5.5.2</h2>
<h2>What's Changed</h2>
<ul>
<li>Fix calculating remaining time across DST changes by <a
href="https://github.com/imrivera"><code>@imrivera</code></a> in <a
href="https://redirect.github.com/celery/celery/pull/9669">celery/celery#9669</a></li>
<li>Remove <code>setup_logger</code> from COMPAT_MODULES by <a
href="https://github.com/rconradharris"><code>@rconradharris</code></a>
in <a
href="https://redirect.github.com/celery/celery/pull/9668">celery/celery#9668</a></li>
<li>Fix mongodb bullet and fix github links in contributions section by
<a
href="https://github.com/jabberwock404"><code>@jabberwock404</code></a>
in <a
href="https://redirect.github.com/celery/celery/pull/9672">celery/celery#9672</a></li>
<li>Prepare for release: v5.5.2 by <a
href="https://github.com/Nusnus"><code>@Nusnus</code></a> in <a
href="https://redirect.github.com/celery/celery/pull/9675">celery/celery#9675</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a href="https://github.com/imrivera"><code>@imrivera</code></a>
made their first contribution in <a
href="https://redirect.github.com/celery/celery/pull/9669">celery/celery#9669</a></li>
<li><a
href="https://github.com/rconradharris"><code>@rconradharris</code></a>
made their first contribution in <a
href="https://redirect.github.com/celery/celery/pull/9668">celery/celery#9668</a></li>
<li><a
href="https://github.com/jabberwock404"><code>@jabberwock404</code></a>
made their first contribution in <a
href="https://redirect.github.com/celery/celery/pull/9672">celery/celery#9672</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/celery/celery/compare/v5.5.1...v5.5.2">https://github.com/celery/celery/compare/v5.5.1...v5.5.2</a></p>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/celery/celery/blob/main/Changelog.rst">celery[redis]'s
changelog</a>.</em></p>
<blockquote>
<h1>5.5.2</h1>
<p>:release-date: 2025-04-25
:release-by: Tomer Nosrati</p>
<p>What's Changed</p>
<pre><code>
- Fix calculating remaining time across DST changes
([#9669](celery/celery#9669))
- Remove `setup_logger` from COMPAT_MODULES
([#9668](celery/celery#9668))
- Fix mongodb bullet and fix github links in contributions section
([#9672](celery/celery#9672))
- Prepare for release: v5.5.2
([#9675](celery/celery#9675))
<p>.. _version-5.5.1:
</code></pre></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/celery/celery/commit/e8adf7f0b4b46a710a96448a9a2f40ace03b4533"><code>e8adf7f</code></a>
Prepare for release: v5.5.2 (<a
href="https://redirect.github.com/celery/celery/issues/9675">#9675</a>)</li>
<li><a
href="https://github.com/celery/celery/commit/2287801006accfa0bba5959bfd2143a6825622d7"><code>2287801</code></a>
fix mongodb bullet and fix contribution github links (<a
href="https://redirect.github.com/celery/celery/issues/9672">#9672</a>)</li>
<li><a
href="https://github.com/celery/celery/commit/1aabeecea57f63802f49d43b6cbd11fb3c33a5f0"><code>1aabeec</code></a>
Remove <code>setup_logger</code> from COMPAT_MODULES (<a
href="https://redirect.github.com/celery/celery/issues/9668">#9668</a>)</li>
<li><a
href="https://github.com/celery/celery/commit/f0c726121468f4368cc6d149a6370900d1b0dbf6"><code>f0c7261</code></a>
Fix calculating remaining time across DST changes (<a
href="https://redirect.github.com/celery/celery/issues/9669">#9669</a>)</li>
<li>See full diff in <a
href="https://github.com/celery/celery/compare/v5.5.1...v5.5.2">compare
view</a></li>
</ul>
</details>
<br />


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