I can't see good handling of time without a cardtype that is for a moment in time. *now already is one, as are the records of the moment of every card addition, edit and update.
*alert could be added to a flexible email, where you give a time (future only of course) when the email will be sent.
*alert could also be a general setting which can send email, play sound, add/edit cards, etc. when the time comes.
add Time cardtype+discussed in support tickets
add Time cardtype+relevant user stories