Not sure I follow this, so a couple things. First, you need a period of total darkness with no daylight or artificial light in the room, and this must be several hours in a block. For most of us who get to bed by midnight, the dark night period would be from say 11 pm or 12 midnight until daybreak. Once the daylight begins entering the room (as it will unless you completely block off the windows somehow) the fish wake up and that ends their rest period. The other essential is to have a continuous block of "daylight" when the tank lighting is on for the benefit of the plants; this can be six hours or seven or eight, or nine...up to you, and usually determined by the biology as you want to discourage algae. Have this "daylight" last when you are normally home to enjoy the aquarium. No point in having the lighting on from 9 to 3 if you are always at work or school or whatever. The periods between the total darkness block and the daylight block represent dawn and dusk to the fish but these can be as long as needed. Just make sure there is ambient room light (whether daylight through the window or artificial room lighting) when the tank light comes on and when it goes off. The ambient lighting should present for an hour minimum at either end.
Example. When I was working I left the house at 6:30am and got back at 6 pm. The tank lights came on at 1 pm and there was obviously ambient daylight even with blinds. Tank lights went off at 9 pm (I was never up much past that, given my schedule) and I had a room light also on a timer to come on just before the tank lighting went off, and remain on for one hour. Then from 10pm until 5 or 6 am it was pitch black.
