Holding down the ctrl-key while dropping a playlist into the calendar view will ignore the position (time) the playlist is dropped and make the playlist automatically chained.
Holding down the alt-key while dropping a playlist into the calendar view will make the playlist remember the time it was scheduled originally.
Holding down the cmd-key while dropping a playlist into the calendar view will make the playlist remember the date and time it was scheduled originally. This is especially helpful in case the playlist has been made offline using a copy of just:play on another system.