Jet lag happens when fast travel across time zones desynchronizes your internal circadian clock from the local day-night cycle, leading to fatigue, poor sleep, and reduced concentration.

How long does jet lag last?

As a rule of thumb your circadian rhythm shifts roughly one hour per day, so a six-hour time change typically takes several days to fully adjust. Eastward travel is usually harder than westward.

Can a planner actually reduce jet lag?

Yes. A structured plan that times sleep, light exposure, and activity in the days before and after a flight can meaningfully shorten adjustment compared with doing nothing.

Is Jet Zzz free to use?

Yes. Jet Zzz is free to use in your browser, with no account required.

Jet Lag from San Francisco to Singapore: How Long & How to Beat It

Jet Lag from San Francisco to SingaporeSingapore runs 15 hours ahead of San Francisco — a eastbound shift over a roughly 17-hour flight. Expect about 15 days to feel close to normal in Singapore.What to expectEastward shifts compress the day and fight the natural drift of the human circadian rhythm, so they tend to feel harder than westward shifts of the same magnitude.Adjustment playbook

Shift bedtime earlier by ~1 hour per day before departure.

Reset your watch to Singapore time at boarding.

On arrival, get bright morning light and avoid bright evening light.

Caffeine in the morning only.

Open in plannerBuild a personalized day-by-day plan for San Francisco → Singapore with your dates, sleep profile, and fixed activities at Jet Zzz.