They should be okay FOR NOW.. If it keeps happening they will get stressed.. And they will hermie.. But seriously just get a timer.. There like ten bucks, and you don't have to worry about it
$5 lowes mechanical timer, be warned I have had mechanical timers fail. $15 digital timer, battery backup, I've never had one fail and you can set the on/off to the second, it's cool to see you lights turn on in sequence at equal time intervals
they'll be fine, but you need to make sure to not skimp on the 12 hours of darkness.
if the lights went off an hour late, turn them on an hour late too so that they still get their 12 hours of darkness. make up for it with an hour less of light if you want to maintain the same lights on and off times.
i used to use timers but not anymore. i haven't missed them by more than a few minutes in either direction though. my body wakes me up now. i am a slave to the plants.