Your body clock is set by when you get up and see light, not by when you go to bed. Move the wake-up time around and the clock drifts, and you end up sleepy at the wrong hours.
Regular sleep timing is linked to better mood, health and daytime function across many studies. Most are observational, so the link is strong and the proof of cause is thinner. It's also a core part of the insomnia treatment that works best. Evidence: decent
Sleeping in after a bad night feels like recovery. It mostly shifts the next night later.
Same theme: The rhythm
The rhythm
The lie-in doesn't pay the debt back
Set this weekend's alarm no more than an hour after your weekday one. Get the missing sleep on ordinary nights, not on Saturday morning.
no timeEvidence: decent
The rhythm
The tracker isn't the doctor
For one week, don't open the sleep score in the morning. Judge the night by how you feel mid-morning.
no timeEvidence: worth trying