Date::Calc [perl]

use warnings;
use strict;

use Date::Calc qw(Delta_Days);

print Delta_Days(2008,8,28,
                 2009,8,28);

365

$ perl -MDate::Calc -e "print Date::Calc::Calendar(2009,5)"

         May 2009
Mon Tue Wed Thu Fri Sat Sun
                  1   2   3
  4   5   6   7   8   9  10
 11  12  13  14  15  16  17
 18  19  20  21  22  23  24
 25  26  27  28  29  30  31