Jet lag is the mismatch between your internal clock and local time. The clock re-entrains at roughly half a time zone to one time zone per day, so a six-hour shift typically takes several days to resolve — faster westward, slower eastward.
Direction matters
- Westward travel requires a phase delay, which aligns with the intrinsic clock's natural tendency. Usually easier.
- Eastward travel requires a phase advance and is consistently harder, particularly for late chronotypes.
A working protocol
- Pre-adapt. Shift sleep and light 30 to 60 minutes per day in the target direction for two to three days before departure.
- Set the watch on boarding and plan sleep against destination time.
- Control light on arrival. Going east: seek morning light at the destination and avoid light in the biological late night. Going west: seek late-afternoon and evening light.
- Nap strategically. Short naps early in the destination afternoon preserve nighttime sleep pressure; long late naps do not.
- Anchor with meals and activity on destination time.
For teams competing on the road
Travel direction, arrival lead time, and competition time relative to biological time all affect readiness. Building this into a travel calendar is one of the highest-yield sleep interventions available to an athletic organization.
Written and reviewed by Christine Mason, PhD, DBSM, health psychologist board-certified in behavioral sleep medicine. Published August 25, 2026. Last reviewed August 25, 2026.