Pardon me for asking stupid questions, but what's wrong with timestamps and localtime()? For instance, to get the date / time of 7 days ago:

my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(t
+ime() - 7*86400);
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If you're going to give an example of what your code can do, it needs to be something that can't be achieved just as easily using built-in Perl functions.