Hi there.

I looked into Your code and the first thought was: "Why doesn't he use timers?"

And when You're on it - You could write an interrupt code that takes care of incrementing Yer counter. Then You can use the main code to do the display and other housekeeping without affecting the counter run.

This would be an excellent project for learning to use interrupts !

Fiddling with delays on main code (for measuring time) is doomed to fail.