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 Sydney: How Long & How to Beat It

Jet Lag from San Francisco to SydneySydney runs 17 hours ahead of San Francisco — a westbound shift over a roughly 14.5-hour flight. Expect about 17 days to feel close to normal in Sydney.What to expectWestward shifts extend the day and align with the natural drift of the circadian rhythm, so most travelers find them easier than eastward shifts.Adjustment playbook

Stay up later than usual the night before.

Stay awake on the plane during Sydney daytime.

Get bright late-afternoon light on arrival; avoid bright morning light day one.

Late-afternoon caffeine is fine.

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