If possible use modules for tricky issues like date/time. You need to worry about daylight saving etc.

#!/usr/bin/perl

my $sixmthb4= time() - ( 24 * 60 * 60 * 30.5 * 6);  # assuming 30.5 da
+ys on avg.
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($six
+mthb4);

print ("Month = ", $mon +1, " Day = $mday, Year = ",$year+1900,"\n");
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