One of the most fascinating magical objects in both the Harry Potter books and the films was the extraordinary clock at The Burrow, home of the Weasley family. The Weasley Clock had nine golden hands, one for every member of the immediate family. Each of those hands was enchanted to always indicate where the corresponding family member currently was, including at home, school, work, traveling, lost, hospital, prison, or in “mortal peril.” Redditor tbornottb3 converted an old thrift store clock to create an awesome working Weasley Clock for his own family.
Instead of magic this clock relies on the IFTTT (If This Then That) web service to enable each of the six members of tbornottb3′s family can use their phones to indicate whatever they like.
“Most of the rules are location-based (setting me to WORK if I enter my university library, HOME if I enter my dorm), but you can set other triggers too (set me to HOLIDAY if the forecast calls for snow, set me to MORTAL PERIL if the stock of the company I’ll be working for next year drops too low) Et voilà!”
Before mechanical clocks, people used candle clocks. Consistently spaced markings indicated the passage of time as the candle melted so people could tell time indoors or at night when the sun wasn’t visible. Source
A candle clock could also be used as a timer by sticking a heavy nail into the candle, which would clatter onto the plate below when the wax around it melted.