BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second by kjmin622 · Pull Request #64836 · pandas-dev/pandas

kjmin622 · 2026-03-25T06:44:53Z

closes BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second #64828 (Replace xxxx with the GitHub issue number)
Tests added and passed if fixing a bug or adding a new feature
All code checks passed.
Added type annotations to new arguments/methods/functions.
Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.
I have reviewed and followed all the contribution guidelines
If I used AI to develop this pull request, I prompted it to follow AGENTS.md.

… 's' and target frequency is sub-second

jbrockmendel · 2026-03-29T20:23:10Z

+
+    def test_round_freq_finer_than_resolution(self):
+        # GH#64828
+        td = Timedelta(1.0, unit="days")


can you assert td.unit == "s"

jbrockmendel · 2026-03-29T20:25:23Z

+            _Timedelta td_ns

        unit = get_unit_for_round(freq, self._creso)
+        if unit == 0:


i think it would be simpler to match the Timestamp._round version:

freq = to_offset(freq, is_period=False) nanos = get_unit_for_round(freq, self._creso) if nanos == 0: if freq.nanos == 0: raise ValueError("Division by zero in rounding") # e.g. self.unit == "s" and sub-second freq return self

jbrockmendel · 2026-03-30T21:56:11Z

 ~~~~~~~~~~~~~~~~~
 - Fixed regression in :meth:`HDFStore.select` where the ``where`` clause on a datetime index silently returned empty results when the index had non-nanosecond resolution (:issue:`64310`)
 - Fixed regression in :meth:`Series.interpolate` where ``limit_direction="both"`` with ``limit`` greater than the Series length raised ``ValueError`` (:issue:`64322`)
+- Fixed regression in :meth:`Timedelta.round`, :meth:`Timedelta.floor`, and :meth:`Timedelta.ceil` raising ``ZeroDivisionError`` for sub-second ``freq`` (:issue:`64828`)


3.0.2 was released today. this will need to be moved to the 3.1 file

…issue64828

kjmin622 · 2026-04-07T07:02:22Z

@jbrockmendel Thank you for your reviews! I applied those.

jbrockmendel · 2026-04-08T16:27:53Z

            ndarray[int64_t] arr

-        unit = get_unit_for_round(freq, self._creso)
+        from pandas._libs.tslibs.offsets import to_offset


can you cimport this at the top?

other than this LGTM. ping on green

@jbrockmendel I moved cimport to the top. Thank you.

jbrockmendel · 2026-04-09T22:31:09Z

+from pandas._libs.tslibs.offsets import (
+    Day,
+    to_offset,
+)


i think to_offset needs to be a cimport or else you get a circular import problem

@jbrockmendel I applied it. Thank you!

jbrockmendel · 2026-04-10T17:36:09Z

thanks @kjmin622

lumberbot-app · 2026-04-10T17:36:33Z

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

Checkout backport branch and update it.

git checkout 3.0.x
git pull

Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 16ca7d9d790698ad433b0982e92ee2846e42650a

You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am "Backport PR #64836: BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second"

Push to a named branch:

git push YOURFORK 3.0.x:auto-backport-of-pr-64836-on-3.0.x

Create a PR against branch 3.0.x, I would have named this PR:

"Backport PR #64836 on branch 3.0.x (BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

jbrockmendel · 2026-04-10T17:39:23Z

@kjmin622 can you handle the backport; follow the instructions above

…-comparison * upstream/main: PERF: use lookup instead of hash_inner_join for merge with unique right keys (pandas-dev#64691) BUG : update `SeriesGroupBy.ohlc()` to honor `as_index=False` (pandas-dev#65141) PERF: Use DataFrame-level reductions in DataFrame.agg with list of funcs (pandas-dev#65031) DOC: document required external libraries in read_* I/O docstrings (pandas-dev#65143) DOC: improve MultiIndex.is_monotonic_increasing/decreasing docstrings (pandas-dev#65154) BUG: Raise ValueError for non-boolean numeric_only in DataFrame/Series reductions (GH#53098) (pandas-dev#65131) BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second (pandas-dev#64836) ENH: Add replace method to Index (closes pandas-dev#19495) (pandas-dev#65099) PERF: improve StringArray.isna (pandas-dev#57733) BUG: read parquet files with older pytz (DEP: keep lower pytz minimum version) (pandas-dev#65133) DEPR: deprecate dates-with-datetime64 in _maybe_downcast_for_indexing (pandas-dev#64871) DOC: note that DataFrame.values is not writeable (pandas-dev#65142) CLN: Update groupby observed defaults (pandas-dev#65148) PERF: avoid materializing values[indexer] in Block.setitem (pandas-dev#64251) DOC: update GroupBy.sum/min/max See Also sections (pandas-dev#65144)

… 's' and target frequency is sub-second (pandas-dev#64836) (cherry picked from commit 16ca7d9)

kjmin622 · 2026-04-13T04:36:24Z

@jbrockmendel I have submitted a backport PR. #65201

…oDivisionError when internal unit is 's' and target frequency is sub-second) (#65201)

…65258)

BUG: Timedelta.round() raises ZeroDivisionError when internal unit is…

e3f7d26

… 's' and target frequency is sub-second

kjmin622 force-pushed the issue64828 branch from 2cfdc97 to e3f7d26 Compare March 25, 2026 06:47

jbrockmendel reviewed Mar 29, 2026

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jorisvandenbossche added Regression Functionality that used to work in a prior pandas version Non-Nano datetime64/timedelta64 with non-nanosecond resolution labels Mar 30, 2026

jorisvandenbossche modified the milestones: 3.0.2, 3.0.3 Mar 30, 2026

jbrockmendel reviewed Mar 30, 2026

View reviewed changes

kjmin622 added 4 commits April 7, 2026 14:33

apply review

cada8e1

Merge branch 'main' into issue64828

9e96fd8

fix CI Test error

1de0549

Merge branch 'issue64828' of https://github.com/kjmin622/pandas into …

85d763c

…issue64828

jbrockmendel reviewed Apr 8, 2026

View reviewed changes

moved cimport up

d3a0c61

jbrockmendel reviewed Apr 9, 2026

View reviewed changes

build error

206af43

jbrockmendel merged commit 16ca7d9 into pandas-dev:main Apr 10, 2026
45 checks passed

lumberbot-app Bot added the Still Needs Manual Backport label Apr 10, 2026

kjmin622 added a commit to kjmin622/pandas that referenced this pull request Apr 13, 2026

BUG: Timedelta.round() raises ZeroDivisionError when internal unit is…

73eb6dd

… 's' and target frequency is sub-second (pandas-dev#64836) (cherry picked from commit 16ca7d9)

kjmin622 mentioned this pull request Apr 13, 2026

Backport PR #64836 on branch 3.0.x (BUG: Timedelta.round() raises ZeroDivisionError when internal unit is 's' and target frequency is sub-second) #65201

Merged

kjmin622 deleted the issue64828 branch April 13, 2026 04:35

jbrockmendel pushed a commit that referenced this pull request Apr 13, 2026

Backport PR #64836 on branch 3.0.x (BUG: Timedelta.round() raises Zer…

4d6c280

…oDivisionError when internal unit is 's' and target frequency is sub-second) (#65201)

jorisvandenbossche added a commit to jorisvandenbossche/pandas that referenced this pull request Apr 16, 2026

DOC: move misplaced whatsnew note for pandas-devGH-64836

2e25c31

jorisvandenbossche mentioned this pull request Apr 16, 2026

DOC: move misplaced whatsnew note for GH-64836 #65258

Merged

jorisvandenbossche removed the Still Needs Manual Backport label Apr 16, 2026

jorisvandenbossche added a commit that referenced this pull request Apr 16, 2026

DOC: move misplaced whatsnew note for GH-64836 (#65258)

64f58c0

hamdanal pushed a commit to hamdanal/pandas that referenced this pull request Jun 27, 2026

DOC: move misplaced whatsnew note for pandas-devGH-64836 (pandas-dev#…

da68d41

…65258)

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kjmin622 commented Mar 25, 2026

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kjmin622 commented Apr 7, 2026

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jbrockmendel commented Apr 10, 2026

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