It’s not true that an hour of sleep before midnight is worth two hours of sleep after midnight.
Sleep needs are much more complicated than that.
The hour of rising is probably much more important in keeping sleep cycles normal.
Individuals go through a series of periods of rapid-eye-movement, or REM, sleep, and non-REM sleep, and both kinds are needed.
There is no evidence that you need more of one than the other, but you do get most of the non-REM sleep in the first three to four hours of sleep and most of the REM sleep after that.
The amounts of different kinds of sleep are determined by when, within a sleep cycle, a person goes to bed and gets up.
A human being’s sleep cycles are also regulated by the amount of sleep needed over a period of several days.
Thus, sleep is regulated both by a system based on “need” for sleep and a system designed to keep the body’s time in synchrony with the time of day, so that others are awake at the same time.
This system allows animal life to be coordinated with the environment, food sources and fellow animals.
The second half of the night is crucially important in setting the rhythm of sleep, and getting up in the morning is the most important act of the day to make sure our biological clocks keep the right time.
It resets the clock.