What about making status effects that are based on the time system, and shut on and off based on what day, week, or month it is.
Example ("That time of the month" when all female wizards lose their powers)
But you could also have some curse happen at the last of every 30 days or so (or full moon). Usually, these status effects should go away by the next day or week, since other stuff shouldn't cure them (inns should be custom here). What do you think?