in reply to
How do I find difference between two timestamps?
Perl's DateTime modules provide an excellent way of dealing with dates and times. Your problem is very similar to one of DateTime's FAQs.
By rote learning.
Via Genetic memory.
It's provided by my firmware.
I just remember them.
Thirty days hath September
My computer gets it right, usually.
I just ask someone else.
Someone punches me on the first of the month.
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