Timer 0 not accurate

[Ioannis]

One second in the ISR is counted as 16.384*62=1.015808

Every minute is 60*1.015808=60.94848 so it is indeed about 50-56 seconds faster.

Why not use the TMR0 as 16 bit timer, no prescaler. After 10000 counts you will have 1 second.

And if you need it to be more accurate you can either use a XTAL 4MHz with a trimmer to adjust it on spot or use the Timer 1 with external xtal at 32.768KHz, divide by 32768 and get 1Hz pulse.

Ioannis

[mfsparky]

I'm sorry I meant that it was 52sec faster every hour not minute. @Richard No I have not defined oscillator but thought it defaulted to 4Mhz. Thanks to you both for your speedy reply. I will define osc and give it ago.

[richard]

I will define osc and give it ago.

that won't help at all, you need to ensure that the config is correct and that osccon reg is set appropriately
define OSC just tells compiler what freq you think you are running at, it does nothing to configure the chip in any way.
and note the OSC bit is case sensitive