How to add timer in program or in-program timer?

Question

Guys, i am working on a program. It is a reminder program, so a remainder must be given while a user explores the other function of the program i want my program to give a remainder a after 10-15min after s starting of the program.
It can be similar to that of CLASH OF CLANS.if you know, like when we give an upgrade it timers for some minutes and it upgrades.
So how to do that in-program timer

Answer 1

Granger but when i do this the program waits until that time.
But instead i want the program to do other functions parallely with the timer!

Answer 2

u can use threading
https://code.sololearn.com/cJgT2G59YaSn/?ref=app