Jet lag and crossing time zones
Jet lag is the mismatch between your internal circadian clock and the local time at your destination. The civil clock jumps as soon as you land; your biology takes days to catch up.
Body clock versus wall clock
Your circadian system expects light, meals, and sleep on a roughly 24-hour rhythm tied to where you have been living. Fly east or west across several zones and local noon arrives hours away from what your body still calls midday.
Eastward travel usually feels harder because you are compressing the day and asking the body to fall asleep earlier. Westward travel lengthens the day and is often easier for the same number of zones crossed.
The severity tracks how many zones you cross and whether you can get morning light at the destination. A three-zone hop is a nudge; a twelve-zone hop is a reset.
What actually helps
Shift sleep and meal times toward the destination a day or two before departure when the trip is long enough to matter. On arrival, seek daylight in the local morning and dim light in the local evening.
Hydration and movement matter more than folklore about which seat defeats jet lag. Avoid stacking alcohol and heavy meals on the overnight flight if you need to be sharp the next morning.
Short trips sometimes do better if you keep home time for sleep and only adopt local hours for meetings — but that only works when the stay is brief and the home offset is not too extreme.
Meetings around travel
Do not schedule high-stakes calls for the morning after an eastbound overnight. Your local clock will say 09:00; your attention may still be on yesterday evening.
Before you fly, convert the agenda once with the converter and write both city times on the invite. Check the destination city page — for example Los Angeles or Paris — so you see the live offset and any nearby daylight saving change.
If teammates stay put while you travel, the meeting time in their city does not move; only your local expression of it does. Anchoring the event in their zone prevents the invite from sliding when you change phones mid-trip.
Try the tools
Frequently asked questions
- How long does jet lag last?
- A common rule of thumb is roughly one day of adjustment per time zone crossed, with wide individual variation. Eastward trips often take longer than westward ones for the same distance.
- Does crossing the International Date Line cause jet lag?
- The date line changes the calendar day, not an extra physiological load by itself. Jet lag still comes from how many hours your body clock must shift relative to local solar time.
- Can I avoid jet lag with melatonin?
- Some travellers use melatonin to nudge sleep timing; evidence and dosing vary, and it is not a substitute for light timing. Treat it as a medical choice, not a guaranteed fix.