DateTime->season?

Hey All,

Someone on the Bricolage list needed a season method, so I whipped up  
this ugly one:

     sub season {
         my $date = shift->strftime('%m-%d');
         return $date lt '03-21' ? 'winter'
              : $date lt '06-21' ? 'spring'
              : $date lt '09-21' ? 'summer'
              : $date lt '12-21' ? 'autumn'
              :                    'winter';
     }

Since seasons can sometimes change on the 22nd instead of the 21st,  
this isn't quite right. Anyone else done something like this but more  
accurate?

Best,

David