I think you're a little confused on how to return data from subroutines. I think this is what you want:

my $date = dateconverter($date_begin);
print $date, "\n";

sub dateconverter {
   my $dateFoo = shift;
   # do stuff here,
   # store your end result in $somevar
   return $somevar; # returns the value
}
[download]

Your $date var will now contain the value of $somevar.

-- vek --