C++ Help

[Endless]

Or convert the time to all seconds and count down against that master number.

That would be simple, wouldn't it? Let's see what the assignment says:

I need tu use a nested loop

I think C++ has a Sleep command.
It's Sleep(int milliseconds) - I think it's in time.h or windows.h .

Similarly...

I (...) can't use pre defined functions to count.

That said, if you can use wait/pause/sleep, use it instead of the for {} loop I used. That's also where you would put a message that displays how much time is left if you wanted.