[Python] Why does pd.to_datetime('2025175', format='%Y%W%w') and...

Why does pd.to_datetime('2025175', format='%Y%W%w') and pd.Timestamp.fromisocalendar(2025, 17, 5) gives different output?

I expected to obtain Timestamp('2025-04-25 00:00:00') for both cases. But the first approach resulted on a Friday one week ahead.

Minimum example

import pandas as pd


friday_datetime = pd.to_datetime('2025175', format='%Y%W%w')
friday_timestamp = pd.Timestamp.fromisocalendar(2025, 17, 5)
assert friday_datetime == friday_timestamp, (friday_datetime, friday_timestamp)


Output:

assert friday_datetime == friday_timestamp, (friday_datetime, friday_timestamp)
AssertionError: (Timestamp('2025-05-02 00:00:00'), Timestamp('2025-04-25 00:00:00'))

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