This sounds pretty simple to achieve without modules. I won't write the code, but here's how I'd do it.

Use time to get the current epoch seconds
Use localtime to convert that to date/time
If the date is greater than 21 
then 
  increment the month number
end
set the date to 21 and the time to 12am
use Time::Local::timelocal to convert that time to 
   epoch seconds
Subtract that from your first number

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In reply to Re: How to get time in seconds from localtime(time) to next 21st date of the month? by davorg
in thread How to get time in seconds from localtime(time) to next 21st date of the month? by basman

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