Rough days to recover (1 day per time zone).
Rough rule: 1 day of recovery per timezone crossed, worse for eastward travel.
Individual variation is huge. Sleep discipline, sunlight exposure, and hydration all matter.
Eastward travel is harder on the body than westward for most people because it requires advancing your internal clock, which is generally more difficult than delaying it — this is a well-documented asymmetry in circadian rhythm research.
6 timezones crossed ≈ 6 days of full recovery.
Adjust sleep schedule 2–3 days before, get morning sunlight at destination, hydrate, avoid alcohol in-flight.
Eastward is harder — you're shortening your day, fighting circadian rhythm. Westward extends the day and usually feels easier.
Many people find recovery gets slower with age, though individual variation is large enough that trip prep and destination light exposure often matter more than age alone.