Datasheet! *sigh*

Timer1 ticks every 1uS @ 4MHz.

It's 16 bits wide, therefore with a 4MHz clock will time 65.536mS between each Flag.

Using the 1:8 prescaler your maximum time is 8*65.536mS=524.288mS

So unless Microchip has shoved hardware into your PIC that mine doesn't have, the answer is NO, Timer1 will NEVER tick 1 second @ 4MHz.

You can always use a Bit Variable as a Flag... If BitFlag=0 and Timer1Flag then half a second has elapsed - so Set the BitFlag. If BitFlag=1 and Timer1Flag then one second has elapsed, so reset the BitFlag and start over for a new Second.

Homework: What has Timer2 got that Timer1 doesn't have?