Date calculation does not take daylight savings changes into account

[Qarj]

Calculating yesterday's date by subtracting 86400 seconds won't work when there are 25 or 23 hours in the day.

There is a solution here by Chas Owens that only uses core Perl modules:

https://stackoverflow.com/questions/3506475/how-do-i-get-yesterdays-date-using-localtime