Originally posted by private1337
I can't set to count down mode when I modify to -1. It prompt me

An unhandled exception has occured in your application. If you click Continue, the application will ignore this error and attempt to continue. If you click Quit, the application will be shut down immediately.

Ticks must be between DatEime.MinValue.Ticks and
Date.Time.MaxValue.Ticks.
Parameter name: ticks

when I Start the timer using the Start button. Any idea?
The program WILL count backwards from a given time if you amend

EndTime += 1

to

EndTime -= 1

I suspect that you amended the Timer.Interval
value to -1 But that should have given you a different error message. Check all of your code carefully with mine.