Physicians and Pharmacists usually say to take drugs at the same time each day so that you get in a habit of taking them so you don't forget. There are some medications that work best when you are asleep, several of the anti-cholesterol medications are best taken before sleep, your liver does the cholesterol dance while you are asleep.
I may be mistaken but I've not heard of any of the female hormones being more effective at night or day, and as Jamie said many of us have implants anyway that release the hormone around the clock.
Contraceptives are usually advised to be used at the same time each day both for the habit and for keeping the hormone levels equivalent on a daily basis, but that is to prevent conception. Usually recommend to be taken in the morning, as many drugs are, because you are less likely to forget in the morning than you are in the evening.