Given a time, how can I find the time one month ago

Question

Given a time, how can I find the time one month ago.

Answer 1

These answers were driving me nuts. You can't subtract 31 days and have a sane result without skipping short months. I'm presuming you only care about the month, not the day of the month, for a case like filtering/grouping things by year and month.

I do something like this:

$current_ym = date('ym',strtotime("-15 days",$ts));