`datetime`: getting the last day of a month

[m-aciek]

Feature or enhancement

Proposal:

Currently to get the last day of the month, the most straightforward method is:

from calendar import monthrange
from datetime import date

mydate = date.today()

mydate.replace(day=monthrange(mydate.year, mydate.month)[1])  # date(2025, 10, 31)

I'd like to propose adding an end_of_month() method to the date class.

• As a class method it would return a last day of month for year and month arguments.
• As an instance method it would return a last day of a month for a date instance.

from datetime import date

date.end_of_month(2025, 11)  # 2025-11-30
date.today().end_of_month()  # 2025-10-31

It can be achieved with a “hybrid method” for Python implementation.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/idea-date-end-of-month/

[abdoulrasheed]

@m-aciek Thanks for opening this and outlining the approach! I'd be interested in giving the implementation a try. Are you planning on submitting a PR, or would you be open to me taking it on?

[gvanrossum]

I don't think this is a reasonable API to add. Unless we also add a whole bunch of APIs for getting e.g. the 3rd Wednesday. But all these strike me as something you probably want to do with some non-stdlib library (and I can't imagine there isn't such a library already).

FWIW I don't follow your recipe. I would write something like

mydate.replace(month=mydate.month%12 + 1, day=1) - datetime.timedelta(days=1)

[StanFromIreland]

I suggest adding this to dateutils instead.

[m-aciek]

Thank you for the feedback.

But all these strike me as something you probably want to do with some non-stdlib library (and I can't imagine there isn't such a library already).

Yes, some of Python datetime third-party libraries have an API for that, e.g. dateutil mydate + relativedate(day=31) and pendulum mydate.end_of('month').

Though I was thinking that this could be a convenience method in the standard library.

For comparison, here are APIs in some of other languages:

language	EOM API	3rd Wednesday API
Java	YearMonth.of(2025, 2).atEndOfMonth()	LocalDate.of(2025, 10, 1).with(TemporalAdjusters.firstInMonth(DayOfWeek.WEDNESDAY)).plusWeeks(2)
JavaScript	new Date(2025, 2, 0)	no API
Oracle SQL	LAST_DAY(MYDATE)	NEXT_DAY(MYDATE - 1, 'WEDNESDAY') + 14

C, C++ and Go don't provide such APIs, C#/Visual Basic provide DateTime.DaysInMonth(dt.Year, dt.Month)).

[hugovk]

Note for JavaScript, January is month zero, day zero means the last of the previous month, and you can go negative as well:

• new Date(2025, 2, 1) -> 1st March
• new Date(2025, 2, 0) -> 28th February
• new Date(2025, 2, -1) -> 27th February
• new Date(2025, 2, 31) -> 31st March
• new Date(2025, 2, 32) -> 1st April

All the parameters can overflow/underflow in this way (reference).

PHP has date("Y-m-t") where t is the number of days in the given month (reference).

[ericvsmith]

I agree that this is best left to third-party modules. Although I don't understand the dateutil example mydate + relativedata(day=31) (which I think should be relativedate).

Maybe advocate getting this into dateutil?

[m-aciek]

Although I don't understand the dateutil example mydate + relativedata(day=31) (which I think should be relativedate).

Oops, fixed. Thank you.

[gvanrossum]

@m-aciek, thanks for contributing and keep them coming!

Given the sentiment among participating core devs and triagers, I'm closing this as "Won't fix".