%formats = (
...
y => [ 's', sub { sprintf("%04d%02d%02d %02d%02d",
                                ( localtime() )[5]+1900,
                                ( localtime() )[4]+1,
                                ( localtime() )[3],
                                ( localtime() )[2],
                                ( localtime() )[1],
                             )
                    }, ], # my own formatstring 
);