timer slightly off .. can i change it?

ok well ive recently noticed that my lights go one like 3:56 (i aim for 4pm) and off at 3:12am (its one of those timers with the little pegs so hard to get it exact..)

can i move the 2nd peg over more to get lights off at 4am without harming my plants? (5 in there)

Yes. Having your plants on a strict light schedule is important, and right now they're sleeping-in 45 minutes more than they need to, which could mean your plants are smaller than they should be. As long as your light turns on @ 4PM, your plants won't be affected by 12 hours of light compared to 11 1/4 hours of light. That will actually show positive effects if anything.

r-e-p'ed+! thanks!