Hi, date math is tricky, not so much because there are no tools, but because one must be very precise in thinking about the calculation actually needed.

If you are asking on, say, March 30, what month is a month ago?

Perl tools differ in their answer: 

$ perl -MDate::Calc=Add_Delta_YM -E 'say "$_ : " . join "-", Add_Delta
+_YM( split("-", $_), 0,-1) for qw/2018-03-28 2018-03-29 2018-03-30 20
+18-03-31/'

2018-03-28 : 2018-2-28
2018-03-29 : 2018-2-28
2018-03-30 : 2018-2-28
2018-03-31 : 2018-2-28

$ perl -MTime::Piece -E 'do { $t = Time::Piece->strptime($_, "%Y-%m-%d
+"); say "$_ : " . $t->add_months(-1)->strftime("%Y-%m-%d") } for qw/2
+018-03-28 2018-03-29 2018-03-30 2018-03-31/'

2018-03-28 : 2018-02-28
2018-03-29 : 2018-03-01
2018-03-30 : 2018-03-02
2018-03-31 : 2018-03-03

[download]
... and that's not even taking into account Daylight Savings Time and other things. So be careful!

(For those wondering, DateTime returns the same as Date::Calc.)

Hope this helps!


The way forward always starts with a minimal test.

In reply to Re: How to get last month date using Date::Calc (caution advised) by 1nickt
in thread How to get last month date using Date::Calc by kanewilliam7777

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