Expiration day is when options expire.
Expiration day is almost always the third Friday of every month. I can't remember a month in the last few years where it did not fall on a Friday, but theoretically Friday could be a holiday.
Anyway, Date::Business helps us out.
#!/usr/bin/perl -w
use strict;
use Date::Business;
#
# usage: $0 MMYYYY
# result: third friday business day of the given month, which
# should be the date equity options expire.
# Use this for equities only;
#
# Bonds and Futures exp dates are another story alltogether.
die &usage unless defined $ARGV[0];
#
# perhaps I should verify $ARGV[0] is an int and
# length($ARGV[0] = 5
#
my $prepassed = $ARGV[0];
my $mon = substr($prepassed, 0, 2);
my $yr = substr($prepassed, 2, 4);
my $passto = $yr . $mon . 21 ;
my $d = new Date::Business( DATE => "$passto", );
while ( $d->day_of_week != 5 ) {
$d->prevb;
}
my $retdate = $d->image();
print("$retdate\n");
sub usage() {
print "\n\t usage:\n\t\tgetExpirationDay.pl MMYYYY\n\t\t";
print "returns expiration day in YYYYMMDD format\n";
}