use strict;
use warnings;

use Date::Manip qw<UnixDate>;
use Date::Parse qw<str2time>;
use Date::Format qw<time2str>;

print UnixDate("12/31/2007", "%L-W%W"), "\n";            # prints "2008-W01"
print time2str("%Y-W%W", str2time("12/31/2007")), "\n";  # prints "2007-W52" (!!)