Once your timer kicks off the light, unplug it and plug it back in when you want it to come on for its new cycle time,

JUST MAKE SURE, that you leave the light off for 18hrs or 24hrs, or whatever it takes to change cycle times.

Having more than 12hrs of darkness, like 24 hrs, to change your on/off times, will be just fine bro😊

Extra darkness the odd day is fine, just cant be less than 12hrs of darkness at night, as that will negatively stress it most likely, so adding hrs of dark to change on/off times is all good🌿