It is recommended that supplemental light be added at the start of the day. The reason for not adding it at the end of the day, is that it is preferred that the poultry get the slowly decreasing natural light at the end of the day so they prepare for the night (roost) normally rather than suddenly being given darkness unexpectedly when the supplemental lights turn off.
What the previous poster said is true, your birds need to have warning that it is getting dark. I do this for my parrot, by having one light on a timer go off 15 min before the other light. I have an African Grey, the one in my Avatar. I add light in the evening and keep her asleep longer in the mornings. I black out her cage in a closet to have enough dark time for her to not lay eggs. You have the same need, controlled lighting to control laying. You want to have at least 14 hours of light to keep them laying, but you also want them to not experience decreasing light. So, you might want to have light in the mornings as well.
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