Subtract n months from datetime

[Cameron Simpson]

On 21Jun2022 17:02, Paulo da Silva <p_d_a_s_i_l_v_a_ns at nonetnoaddress.pt> wrote:
>I have a datetime, not a date.

Then you need a date. I would break the datetime into a date and a time, 
then do the months stuff to the date, then compose a new datetime from 
the result.

>Anyway, the use of calendar.monthrange simplifies the task a lot.

Hmm, yes it would.

The important thing to remember about any solutions mentioned is that 
dates and datetimes have different semantics. Specificly, you can't add 
fixed elapsed times such as seconds to do "calendar like" arithmetic, 
which works in days etc because months have varying numbers of days, and 
days have varying numbers of seconds (not merely the odd leap second but 
also the horrors of timezones and summer/winter time shifts).

So working with the calendar component (days upwards) is a meaningful 
thing. But working in, say, seconds with the _bjective_ of doing days or 
months is nearly pointless.

Cheers,
Cameron Simpson <cs at cskk.id.au>