Different people have different cycles where they are alert and productive. About 2/3 of the population are "larks", most alert in the morning, go through a trough in the arternoon and return to some sort of creative/productive state in the early evening. About 1/3 are owls. They have their trough in the morning, the creative/productive phase during the day and the alert phase in the evening.

It's good to be aware of what type you are and what works for you. Conversely, recommending anyone just gets up earlier may be more harmful than helpful, depending on the person.