Jet Lag Recovery Calculator (Time Zones & Adjustment)

Jet Lag Recovery Guide

Why Jet Lag Happens?

Jet lag occurs when your internal body clock (circadian rhythm) is out of sync with the local time at your destination. Your body clock controls: sleep-wake timing. Hormone release (melatonin, cortisol). Body temperature rhythm. Digestion and appetite. Alertness and performance. When you cross time zones rapidly, your internal clock stays on home time while the external environment is on destination time. Symptoms: difficulty sleeping at night, sleepiness during the day. Fatigue and grogginess.

What's the difference between East and West?

Direction dramatically affects jet lag severity. Eastward travel (UK → Asia, Australia): you 'lose' time — must go to sleep and wake earlier than your body wants. Harder to adjust. Your body must advance its clock. Recovery: roughly 1 day per time zone, sometimes more. Westward travel (UK → USA): you 'gain' time — stay up later and wake later. Easier to adjust. Your body delays its clock (which it does naturally). Recovery: roughly 2/3 day per time zone crossed westward. Why: the human circadian rhythm naturally runs slightly longer than 24 hours, making it easier to delay the body clock westward than to advance it eastward.

What do I need to know about Light Exposure Strategy?

Light is the most powerful tool for resetting your body clock. Light tells your brain when it's 'day'. Timing light exposure correctly shifts your clock in the desired direction. Eastward travel (advance clock — need to wake earlier): seek morning light at destination (advances clock). Avoid bright light in the evening (would delay clock). Get outside in the morning sun on arrival. Westward travel (delay clock — need to stay up later): seek evening light at destination (delays clock). Avoid early morning light on the first day or two after westward travel, since this can inadvertently reinforce the old time zone rather than helping the body adjust to the new one.

What should I know about Practical Strategies?

Before you travel: gradually shift sleep schedule 2-3 days before (1 hour/day toward destination time). Arrive rested, not sleep-deprived. During the flight: set your watch to destination time on boarding. Sleep according to destination night (use eye mask, earplugs). Stay hydrated, avoid excess alcohol and caffeine. Move around periodically. On arrival: adopt local schedule immediately (eat, sleep, wake on local time). Get outside in daylight at the right time (see light strategy). Avoid long naps on arrival day, even when exhausted, since sleeping for hours during local daytime can significantly slow the adjustment to the new time zone.