What about Date::Parse?
in reply to Converting dates later than 2038 into epochseconds
Update: Do you negitive numbers for dates before 1970?
Update: I did a little testing of this and it won't work for your needs. Sorry for the bum suggestion. Oddly enough it will give you answers for dates before 1970 if that helps.
$date = "Aug, 20 1955 11:09:55 +0100";
$time = str2time($date);
print " $date\n";
print " $time\n"
# perl tmp.pl
Aug, 20 1955 11:09:55 +0100