I am looking for ways to tell time when the sky is completely blacked out all the time.

I am aware of nails and other metal objects inserted into candles. Due to vegetation dying due to this calamity, sources of candle making materials could be in short supply. Such as: bees, animal fat,uhh human fat.

Magic is rare, but available, to alleviate some problems.

Godly given magic is also a rare commodity as worshiping souls are becoming more and more rare.