Most of us moderns sleep monophasically. That is to say, we sleep in one big chunk at night. This is not what the Buddha did and not what the vinaya (the rules for monks and nuns) suggests. The Buddha slept in one approximately four-hour chunk in the middle of the night. He went to be late and got up very early. But he also took a sizeable nap during the day. Read more about Buddhism and sleep here and here and here and here.
This might seem weird, but historically it’s quite common and actually very practical. Remember where the Buddha was: a very hot country with no air conditioning. Why was siesta such a popular idea in Spain and Latin America, and why is it falling out of favor now? The same reason why places like Singapore and Hong Kong have become world financial sectors only in the last half century. It’s the reason Phoenix and Houston are growing while the rust belt is shrinking. In a word, air conditioning. You can’t trade stocks in a coat and tie in 110 degree heat. It made a huge amount of sense to nap in the hottest part of the day when you live in a country that hot. It is hard to work (and not very efficient) in the heat of the day. Also, the closer you live to the equator, the more daylight you have in certain parts of the year. If you are going to sleep 7 hours anyway, it makes sense to be alert in the cooler morning and evening times and sleep through the miserable heat.
Besides, like so many of the things that the Buddha did, there is growing evidence that he was on to something. The Buddha advised eating once a day for health reasons. There is a growing body of evidence that this is highly beneficial. I currently do it most of the time myself. There is also growing evidence that napping is a great idea. For example.
There are actually many possible sleep patterns, all of which can be made to work. While mono- and biphasic are the most common, there are also polyphasic sleep patterns. Edison famously napped throughout the day. Buckminster Fuller supposedly did Dymaxion, a sleep pattern he invented with four equal naps arranged evenly throughout the day. Uberman polyphasic sleep means taking 6 20-minute naps throughout the day. It sounds impossible, but I tried it for about nine months, and it worked very well. I only gave it up because my wife finally put her foot down about having me bumping around the house all through the night. I also noticed that it wasn’t especially great for my meditation practice. I had more time but not a more peaceful mind. I also tried the easier Everyman, with 4 sleeping periods arranged as three 20-minute naps and one 3-hour snooze. It worked as well.
People in the past generally did not sleep as we do. For one thing, they had far less light to work with than we did. I have a little yurt in the woods that has no electricity. Without electric lights, night is usually DARK. It’s profoundly dark in a way that most modern people never really experience at all. And candles, even good candles, are way more dim than even a pocket flashlight. Before the industrial revolution, even candles were expensive luxuries that only the 1% of their day could afford. The long and short of it was that we went to bed earlier, slept more, and were more likely to wake up in the middle of the night. It turns out this is probably something like the typical sleeping pattern for most people before lighting. For more about Roger Ekirch’s work in this area see this.
The moral here is that people’s sleep patterns are very flexible and change a lot based on circumstance. The aim of the Buddha is was always to lead a better life aiming for liberation. If that is your aim as well, consider his sleep recommendations.