Countdown timer for on-call, both leading up to and during

[Wenike]

Hello everybody! Does anybody know of any sort of module that will do a countdown timer that I’m hoping to use for being on-call. It’d show how long until I go on-call, then flip to how long until I’m not on-call and then back to how long until on-call again. Preferably calendar events but also could work with some sort of simple file import. If it helps, its a fairly regular schedule of on-call for one week out of 11 weeks in the rotation too.