When I use Timer2, I tend to setup a 10mS period and count 100ths of a second. To do this you set timer2 to prescaler=4, postscaler=10 and pr2=250. This gives a period of 4*250*10=10,000uS = 10mS.
When I use Timer2, I tend to setup a 10mS period and count 100ths of a second. To do this you set timer2 to prescaler=4, postscaler=10 and pr2=250. This gives a period of 4*250*10=10,000uS = 10mS.
That system automatically factors in all overheads AND self corrects them.
But for clocks it's main beauty is that the 1 second is derived from a single value constant, so you can just "tweak" that one constant to perform any xtal compensation you like, for example adding a few parts per million to make the clock more accurate.