AM = morning, PM = afternoon/evening/night

Like 7AM or 7PM

AM people are most awake and productive during the morning hours, and get more tired as the day goes on.

PM people are tired in the morning and more alert later in the day/night.

I'm sure there's numerous potential reasons for it. Some may be relying on the consistency of their sleep schedule more than others, have responsibilities that reduce how much they can reasonably fit in their schedule, may not care about the quantity or quality of sleep they get, have a pre-existing sleep debt, have health issues that compound with sleep changes, alternative sleep schedules, genetic predispositions, or literally anything else related to how sleep, physical health, mental health, and bodily systems function.

If you think of how one thing being shifted can set other things way more off balance then it makes sense. I'm not an expert in any of this but it's definitely a complicated topic at the very least.

I would refer back to my peanut butter comment. Or bee stings. Or celery.

Some people are near-sighted. Some have asthma. ADHD. Some have 12 toes. Or two penises.

People are genetically diverse. They just are.

Maybe you don't, but other people do. "I don't have that problem" isn't an excuse to not do anything about it.

Saapas, I can see that you were trying to relate your own experiences to the discussion and even add to the discussion by asking a question. I'm sorry that nobody seems to understand what you're trying to do. Many here are autists and many more are self-involved. I, in fact, am both and very pleased with myself for feeling empathy and compassion in this moment.

Back to your very valid question: Sleep scientists have long tracked sleeping cycles. Not all sleep is equal. Sleeping for a certain amount of time resets certain chemical imbalances in the brain. Many people can take a twenty-minute nap at midday, for example, and feel clear-headed afterwards. However, if they take an hour nap, they may feel lethargic. But then maybe that same person could take a two-hour nap instead, and feel great.

Your mileage may vary, but my point is that sleep cycles are a real thing. If your body is used to going to sleep at a certain time, that's the time it expects sleep. It's based on your body's own internal clock. Daylight Savings Time messes with that clock. Your body doesn't care that your phone jumped ahead an hour.

Not everyone will have a difficult time adjusting, but it's not uncommon to feel restless for a couple of weeks until the body catches up to the new sleep pattern.

https://letmegooglethat.com/?q=circadian+rhythm+daylight+savings