It depends on what they currently get. If you have them in a room with windows, thats is "natural light". That is currently reducing the photoperiod naturally (because it's near winter). If you also use a tank light, how long do you keep it on? Cut back by 1 hour every 2-3 days of your tank light. Until you get to around 8 hours total. If their is a lot of natural light in the room (many south facing windows), nix the tank light altogether, or for just an hour around feeding time.
I have all my lights on a timer. I allow 3-4 hours of morning light from the window, then the tank lights come on for a period of time, then shut off. In the summer I keep the total photo period to around 12 hours. In the winter it is around 8 hours.
Feed them minimally as well. If you feed 3 times a week, cut back to 1-2 times. Do this for 4-6 weeks and then gradually increase the total photo period time. I usually do a water change, and add 1-2 more inches of water from the original water line on the tank during refilling. I feed 3-4 times a week and give them a variety. What you are doing is creating "spring time", rainy, increased water, warmer, more light, and lots of food. Each species is different. Spanish ribbed newts, just need a good water change, and an increase in food and that seems to work. Some newts need a hibernation period of very low temperatures, where the keepers pack them away in wet moss in their refrigerator. It really depends on the species and their natural history. Good luck.
Al
