PIC18f4550 Timer setup for 1sec Interrupt
Timer 0 is not well suited to long but precise periodic interrupts.  You can do short interrupts by using timer 0 in 8 bit mode with a presscaler of 1, but those are limited to 256 cycles.  You also have to understand the timer very well to not loose any cycles each period.  

Timer 2 is a better answer since it has a built-in period register.  Perhaps you can't get a time as long as 1 s, but that can be easily created by counting a number of faster but accurate timer 2 interrupts.  At the least you can set up timer 2 to interrupt every few 1000 cycles, so the overhead of counting a few of those before you get to 1 second is noise.