This crops up when people use timers in apps that run for days and weeks.
They want to know how long the app has been open, or time between two points.
A single Integer (no matter how large) is not good for this because sooner or (much) later it overflows and you end up with an apparent ‘used for - 3000 years’
If you need such a timer, create a method or class that has a value for Days_Elapsed as UINT64 or even a double.
Have your timer by all means, but once it reaches a value that means 24 hours, go increment the days counter, and reset your ticks/seconds variable to 0
Doing it that way means you will not overflow before the Sun explodes.