Planted Tank Obsessed
Join Date: Sep 2012
Location: Mpls, Minnesota
Unless you have particularly sensitive plants I'd say just go ahead and switch to your new lighting schedule tomorrow (or whatever day is most convenient to you). The plants won't be harmed by one weird extra long night and as long as the photoperiod is similar they will adjust very quickly. Right now I'm on a 3PM-10PM light schedule too (I reduced it by an hour because of algae growth and this is going better).
One thing to keep in mind with a lighting schedule like this is you'll want to reduce ambient sunlight that may fall on the tank. That does add to the overall lighting hours and can cause issues. I keep the blinds closed tightly on the tanks near windows.