Finally, after months of disrupted sleep, I have reverted back to sleeping 12am - 8am.
I have been going to bed at midnight for at least 30 years and waking at 7am.
Since I retired 4 years ago I now wake at 8am. New normal.
But since I returned from my overseas holiday in October my sleep pattern has been erratic, only getting 3-4 hours longest period and laying awake till all hours. Since Christmas I got in the habit if I was awake for more than 1 hour I would get up and potter around the house or read.
No energy and no inclination to do any thing during the day.