You are referring to the 12L/12D schedule (twelve hours of light and twelve hours of darkness) that we used to use years ago and that, unfortunately, some people are still recommending even though we have since learned that parrots will produce sexual hormones all year round when kept that way. Basically, you can't put him to bed at any arbitrary hour (7 pm or whatever you choose), he has to go to bed with dusk and, this time of the year, the sun is halfway down to the horizon at 3:30 pm so that is the time that the artificial lights need to be turned off and, if you do, he will fall asleep when it's completely dark (around 5 pm). The special light that happens at dawn and dusk are the triggers for their internal 'stop watch' that measures day length. In the morning, with the dawn light, the stop watch is turned on and, when they are exposed to the dusk light, it gets turned off - and the number of hours in between these two events is what tells their body whether they should start sexual hormone production or shut it off. If you only expose him to dawn and not dusk, his body will continue been confused... and it's not only a matter of sexual hormones production, the endocrine system is connected to the immune system and it also regulates sleep quality, appetite, molt, mood, and a million other things.