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@jbrockmendel jbrockmendel commented Dec 12, 2025

to_datetime analogue of #63303.

@jorisvandenbossche jorisvandenbossche added Non-Nano datetime64/timedelta64 with non-nanosecond resolution Timestamp pd.Timestamp and associated methods labels Dec 18, 2025
@jorisvandenbossche jorisvandenbossche added this to the 3.0 milestone Dec 18, 2025
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Looks good!

errors=errors,
unit_for_numerics=unit,
creso=cast(int, NpyDatetimeUnit.NPY_FR_ns.value),
# creso=cast(int, NpyDatetimeUnit.NPY_FR_ns.value),
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cleanup?

Comment on lines 906 to +908
>>> pd.to_datetime([1, 2, 3], unit="D", origin=pd.Timestamp("1960-01-01"))
DatetimeIndex(['1960-01-02', '1960-01-03', '1960-01-04'],
dtype='datetime64[ns]', freq=None)
dtype='datetime64[s]', freq=None)
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This makes me wonder about a potential corner case: what if the original actually has values for a lower resolution, like actual microseconds or nanoseconds?

Comment on lines +1315 to +1318
# Without this as_unit cast, we would fail to overflow
# and get much-too-large dates
return to_datetime(new_data, errors="raise", unit=date_unit).dt.as_unit(
"ns"
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I am not directly understanding that comment. new_data are integers here? Why does the return unit of this function need to be nanoseconds? (to preserve current functionality?) Why would this give (wrong?) too large dates?


result = read_json(StringIO(json), typ="series")
expected = ts.copy()
expected = ts.copy().dt.as_unit("ns")
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Not for this PR, but so this is another case where we currently return ns unit but could change to use us by default?


index = pd.MultiIndex(
levels=[[1, 2, 3], [pd.to_datetime("2000-01-01", unit="ns")]],
levels=[[1, 2, 3], [pd.to_datetime("2000-01-01", unit="ns").as_unit("ns")]],
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Did this PR change that? (that this no longer returns nanoseconds)

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2 participants