[Python] Why can Pandas weekday DateOffset only move the date forward?

I am trying to find the last of a weekday in a month. For example, let us say the last Sunday in October.

I try to do like this:

pd.Timestamp("2025-10-31") - pd.DateOffset(weekday=6)


The resulting date is Timestamp('2025-11-02 00:00:00'), i.e. the result is a later date despite the minus. The result is also identical if I add in stead of subtract.

This is in contrast to:

>>> pd.Timestamp("2025-10-31") - pd.DateOffset(days=2)
Timestamp('2025-10-29 00:00:00')

>>> pd.Timestamp("2025-10-31") - pd.DateOffset(day=2)
Timestamp('2025-10-02 00:00:00')


which result in an earlier date as I expect, so the behaviour is just different for 'weekday' than for other offsets.

If I attempt to use the DateOffset.rollback method instead, it simply does not change the date:

>>> pd.DateOffset(weekday=6).rollback(pd.Timestamp("2025-10-31"))
Timestamp('2025-10-31 00:00:00')


I cannot find anything in the DateOffset or DateOffset.rollback documentation that describes this.

What can I do to make this work?

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