Jet lag occurs when your internal body clock (circadian rhythm) is out of sync with the local time at your destination. This happens because your body's natural 24-hour rhythm — regulated by light exposure, melatonin, and other factors — cannot instantly adjust to a rapid time zone change. Symptoms include fatigue, insomnia, difficulty concentrating, digestive issues, and general malaise. The more time zones you cross, the more severe jet lag tends to be, especially when traveling eastward.

Light is the single most powerful cue for regulating your circadian rhythm. Specialized cells in your retina detect light and send signals to the suprachiasmatic nucleus (SCN) — your brain's master clock. Morning light exposure advances your internal clock (helpful when traveling east), while evening light exposure delays it (helpful when traveling west). The timing, intensity, and duration of light exposure determine the direction and magnitude of the shift. Strategic light exposure can speed up adjustment by 1-2 hours per day.

When traveling east (e.g., New York to London), you need to advance your circadian rhythm. Seek bright light exposure in the morning hours (7:00 AM – 11:00 AM) at your destination. This helps shift your body clock earlier. Avoid bright light in the late afternoon and evening (after 4:00 PM), as this could delay your rhythm and counteract your adjustment. Continue this pattern for 3-5 days after arrival for the best results.

When traveling west (e.g., London to New York), you need to delay your circadian rhythm. Seek bright light exposure in the late afternoon and early evening (3:00 PM – 7:00 PM) at your destination. Avoid bright light in the morning hours — wear sunglasses if you go outside before midday. This pattern helps push your internal clock later, aligning it with the local schedule. Follow this protocol for 2-4 days post-arrival.

As a general rule, your body adjusts at a rate of about 1 time zone per day when traveling east, and about 1.5 time zones per day when traveling west. This means a 5-hour time difference flying east might take 4-5 days, while the same difference flying west might take 3-4 days. Using strategic light exposure, melatonin supplements (consult a doctor), and maintaining good sleep hygiene can accelerate this process significantly.

Research suggests that 10,000 lux is the gold standard for light therapy. Outdoor sunlight provides this easily — even on an overcast day, you'll get 10,000-25,000 lux. A dedicated light therapy lamp delivering 10,000 lux at a distance of 30-60 cm (12-24 inches) is the recommended indoor alternative. Sessions typically last 30-120 minutes. Lower intensities (2,500-5,000 lux) can work but require longer exposure times.

Melatonin can be a helpful supplement for jet lag when used correctly. Take 0.5-5 mg about 30 minutes before your target bedtime at the destination. Melatonin helps signal to your body that it's time to sleep, especially useful when traveling east. For westward travel, melatonin may be less necessary since the natural delay is easier. Always consult with a healthcare provider before starting melatonin, especially if you take other medications or have health conditions.

Yes! Pre-adjustment can significantly reduce jet lag severity. Start shifting your sleep schedule 2-3 days before departure: if flying east, go to bed 30-60 minutes earlier each night; if flying west, stay up 30-60 minutes later. Adjust your light exposure accordingly — seek morning light before eastward trips and evening light before westward trips. Also, stay well-hydrated, avoid alcohol during the flight, and move around the cabin regularly.

Flying east is generally harder because it requires shortening your day — going to bed earlier than your body expects. The human circadian rhythm naturally runs slightly longer than 24 hours (about 24.2 hours), making it easier to extend a day (westward travel) than to compress one (eastward travel). This is why the rule of thumb is 1 day per time zone for eastward recovery vs. 0.7 days per zone for westward.

For very large time differences (8+ hours), consider whether the reverse strategy might work better. For example, a +14 hour difference (eastward) can be treated as a -10 hour westward adjustment — sometimes a more natural direction for your body. Our planner detects this and provides an alternative recommendation when appropriate. Choose the direction that feels more manageable for your schedule and body.