The game clock time tracker for tabletop roll playing games works much like any sort of alarm clock, only instead of running on real world time, it runs on the time of your roll playing game world. You can set various alarms and timers, and then advance the clock based on what is going on on the table - be it rounds of combat, exploration, or resting in town.
There are two parts to the game clock - the current time (displayed as a clock), and the various alarms and timers. The clock is advanced manually by selecting the duration of time that passes, or explicitly editing the time time to a new time (the time editor supports adding and subtracting amounts of time, if, for example, you need to spend 10 hours, 3 minutes, and 13 seconds doing something).
Time is all based on a relative “number of days”. So it starts at “day 1”, and advances from there. This allows times to work independent of whatever underlying calendar system is used in the game world.
There are three kinds of alarms/timers:
When any of the alarms go off, the bell icon in the view will appear - if a repeating one goes off multiple times, that is also indicated, so you will know how many checks for wandering monsters need to happen in that short rest.