Why is Monday so hard? Measure your weekend drift.

How this works

Social jet lag is the gap between the clock your work week asks for and the clock your free days drift toward. The simplest version is the difference in wake times. If you also know bedtimes, midsleep — the midpoint of the night — is a slightly fuller picture.

The body clock is more willing to stay up late than to get up early, which is why a long weekend lie-in can make Monday morning feel unfair. That is not a moral failing. It is a timing mismatch.

A useful starting point is to keep your wake time within about an hour, every day, including weekends. If the gap is larger, you do not have to jump all at once. About 30 minutes earlier each weekend, plus daylight soon after waking, is a gentle way to close it.

If weekends are when you finally catch up, the weekday side may be running short. The meter will mention that without turning it into a score.

Questions people ask

What is social jet lag?

It is the shift between your weekday sleep timing and your weekend timing. The clock in your body treats that a bit like travelling across time zones, even if you never left home.

Is sleeping in on weekends bad?

A little later is common and often fine. When the lie-in grows past about an hour, Monday can feel heavier because your clock has moved.

How much weekend lie-in is okay?

Staying within about an hour of your weekday wake time is a healthy range to experiment with. Protect the window, not the exact minute.

Why do I feel jet-lagged without travelling?

Late nights and late mornings on free days shift your body clock. Returning to an early weekday alarm then feels like a small eastbound flight.