Have you noticed that everyone is starting to work weirder hours--not you, of course. It depends on your organization, sure. But let's look around; emails are coming in earlier, and later.
Years ago I heard about an experiment to determine what a humans "natural" biorhythms are. They took a scientist and put her deep into a completely light starved cave. They gave her a computer and control over her own artificial lighting. She had communication with the outside world when she wanted it, but all reference points as to time of day were completely cut off. As a result, her days got longer and longer, and so did her sleep cycles. Eventually, she was up to 24 hour days and 24 hour nights: a 48 hour "day". Here's a related event.
Now look at your own performance over the last month. You may be noticing that you are having weird work stints far into the night....and the inexplicable need to sleep during inconvenient work hours. My hypothesis is this: humans derive their wakefulness and sleep patterns not only from light (as in the above-referenced experiment) but also from socialization. We are all cooped up one way or another, ergo our waking and sleeping lives are expanding.
What to do?
Here is what I'm doing:
1. I'm running with it. I sleep when I'm tired and I work when i want to. So I'm getting up when my colleagues expect me to, check my email (I have to) then sleep more until I'm ready. Then I get up and start my day. The day runs deep into the night and that's cool.
2. When I feel really tired, I take a rest. Naps aren't working too well at distraction, but listening to documentaries is helping. Better than binge-watching "N.C.I.S."--that got old.
3. I'm communicating clearly with colleagues about when I'm available and when I'm not.
4. I'm scheduling my meetings around what I need, not around what I've always done.
5. I'm working out like hell at least once a day (yep, in my living room) and eating better than ever. Here's the blog of my favorite trainer.
You can beat this. But you can't do it trying to cram your new experience into your old routine. Adapt!!! Here are more ideas on how to help yourself adapt.