Westbound vs Eastbound Jet Lag: Why Direction Matters

The human circadian rhythm runs on a cycle of roughly 24.2 hours, drifting later. Westward travel matches that drift; eastward fights it.

Westbound playbook

Stay up later. Bright light in the late afternoon at the destination. Avoid bright morning light for the first day or two. Late-afternoon caffeine is fine.

Eastbound playbook

Bedtime earlier in the days before. Bright morning light at the destination, avoid bright evening light. Caffeine in the morning only.

When direction stops mattering

For shifts of 12+ hours, direction-specific tricks fade. Focus on the destination clock.