in reply to
my $tm = localtime;
my $this_month = sprintf("%04d%02d?", $tm->year+1900, ($tm->mon)+1);
my $last_month = ($tm->mon == 0)
? sprintf("%04d12?", $tm->year+1899)
: sprintf("%04d%02d?", $tm->year+1900, $tm->mon);
By rote learning.
Via Genetic memory.
It's provided by my firmware.
I just remember them.
Thirty days hath September
My computer gets it right, usually.
I just ask someone else.
Someone punches me on the first of the month.
Results (144 votes),