Ah you thought they did it like:

if ( date == target_date ) { \ do the thing }

But it was really:

time_to_target = convert_date_to_time_to( target_date ); // always returns the closest time to whatever date you specify (even if the date doesn't exist (March 31st does exist))
do_thing_in_x_time( the_thing, time_to_target );