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Reproducible Example

import pandas as pd dt = pd.to_datetime(['2024-02-24 10:00']) s = pd.Series([1],index=dt) s.loc['2024-02-24 9:57'] = None # is inserted into s print(s) s.loc['2024-02-24 10:2:30'] = None # is inserted into s print(s) s.loc['2024-02-24 10:08'] = None # is _not_ inserted into s print(s) s.loc['2024-02-24 10:08:00'] = None # is inserted into s print(s)

Issue Description

When inserting timestamps into a pandas Series, beginning with the format 'yyyy-mm-dd hh:mm', they are inserted correctly, until first time switching to format 'yyyy-mm-dd hh:mm:ss'. From then on format 'yyyy-mm-dd hh:mm' is silently not inserted, ending with seconds required.

Not sure if this is intended, unexpected behaviour in my opinion.

Expected Behavior

Insert timestamps as long as their format is parsed unambiguously.

Installed Versions