The best way to prepare for travel across time zones is to start shifting your sleep schedule a few days before your trip, then use light exposure and meal timing strategically once you arrive. How much preparation you need depends on the direction you’re traveling and how many time zones you’ll cross. A general rule: it takes about one day to fully adjust per time zone crossed, and flying east is harder than flying west.
Why Time Zone Changes Feel So Rough
Your body runs on an internal clock that coordinates everything from sleep and hunger to hormone release and body temperature. When you cross time zones quickly, the external light cycle suddenly shifts, but your internal clock doesn’t move with it. The result is a temporary mismatch: different systems in your body adjust at different rates, so your sleep signals, digestion, alertness, and mood are all briefly running on their own schedules. That’s why jet lag isn’t just about being tired. It can also cause stomach issues, difficulty concentrating, and a general feeling of being “off” for days.
Flying east is typically harder because you’re asking your body to fall asleep earlier and wake up earlier, which works against the clock’s natural tendency to drift later. Flying west, where you gain hours, is more forgiving because staying up a bit longer feels more natural to most people.
Shift Your Sleep Schedule Before You Leave
The simplest thing you can do before a trip is gradually nudge your sleep and wake times toward your destination’s time zone. The CDC recommends starting a few days before departure:
- Traveling east: Go to bed one to two hours earlier than usual each night.
- Traveling west: Go to bed one to two hours later than usual each night.
Even two or three days of this can meaningfully reduce the shock when you land. You don’t need to fully match the destination time before you leave. Just closing the gap by a few hours gives your body a head start. Pair this with shifting your meal times in the same direction, since eating signals also help reset your internal clock.
Use Light Exposure Strategically
Light is the single most powerful tool for resetting your body clock, and timing it correctly matters more than anything else you do. The key principle: bright light in the morning pushes your clock earlier (helpful after eastward travel), while bright light in the evening pushes it later (helpful after westward travel).
For eastward travel, seek bright light in the early morning and avoid it in the evening. Open the window shade on the plane if you’re arriving in the morning, skip sunglasses when you step outside, and dim your environment after sunset. For westward travel, do the opposite: avoid bright light in the early morning (keep curtains closed, wear dark sunglasses if you’re outside) and get as much evening light as possible.
This applies on the day of travel and for the first few days at your destination. If you get the timing wrong, especially by exposing yourself to bright light during the wrong window, you can actually push your clock in the opposite direction and make jet lag worse. A simple guideline: think about whether you need your body to shift earlier or later, and use light accordingly.
How Melatonin Can Help (and When It Backfires)
Melatonin is one of the most studied supplements for jet lag, and it works well when used correctly. A large review of clinical trials found that doses between 0.5 and 5 milligrams are effective for flights crossing five or more time zones. Higher doses don’t work better than 5 milligrams, so starting with 2 or 3 milligrams is reasonable for most people.
The timing matters more than the dose. Take it at your destination bedtime, between 10 p.m. and midnight, after it’s already dark. Start on the first evening of travel or arrival and continue for a few nights. Taking it earlier in the day can cause unwanted drowsiness and actually delay your adjustment, the opposite of what you want.
One important note from the research: taking melatonin before your day of travel doesn’t speed up adaptation. Save it for arrival.
What to Eat and Drink (and What to Avoid)
Meal timing acts as a secondary clock-setting signal. The simplest approach is to start eating on your destination’s schedule as soon as possible. If it’s breakfast time where you’re headed, eat breakfast, even if your body thinks it’s 2 a.m.
A more structured approach, originally developed at Argonne National Laboratory and tested on military deployments across nine time zones, involves four days of alternating between high-calorie and low-calorie days before travel. On high-calorie days, you eat protein-rich breakfasts and lunches with a carbohydrate-heavy dinner. On low-calorie days, you limit intake to about 800 calories, mostly fruits and vegetable soup. The day of travel is a fasting day, and you eat a large protein-rich meal at your destination’s breakfast time upon arrival. This protocol showed benefits in military studies, though it requires planning and discipline that may not be practical for every traveler.
Caffeine deserves special attention. A dose of caffeine taken three hours before your normal bedtime can delay your internal clock by about 40 minutes. That’s roughly half the effect of bright light exposure. This means caffeine in the afternoon or evening after eastward travel can actively slow your adjustment. Use coffee strategically in the morning to boost alertness, but cut it off by early afternoon at your destination.
Alcohol disrupts sleep quality even in small amounts and interferes with the clock-resetting process. Avoiding it for the first day or two after arrival gives your body the best chance to adjust cleanly.
Your First Days at the Destination
Once you arrive, the goal is to lock into local time as quickly as possible. Get outside during daylight hours, eat meals on the local schedule, and go to bed at a normal local time, even if you’re not tired yet. Resist the urge to crash for hours upon arrival if it’s still daytime. If you absolutely need to nap, keep it to 20 or 30 minutes and do it before mid-afternoon. Longer naps or naps later in the day will push your adjustment backward.
Recovery follows a roughly predictable timeline. Most people adjust at a rate of about one time zone per day. A five-hour time difference means about five days to feel fully normal, though you’ll notice significant improvement after the first two or three days. Eastward trips tend to take longer than westward trips of the same distance.
A Pre-Travel Checklist by Direction
Heading East
- 3 to 4 days before: Move bedtime earlier by one to two hours per night.
- Morning of travel: Get bright light as early as possible.
- Evening before and during travel: Avoid screens and bright light after sunset.
- On arrival: Take 2 to 3 milligrams of melatonin at local bedtime. Seek morning sunlight the next day.
Heading West
- 3 to 4 days before: Move bedtime later by one to two hours per night.
- Morning of travel: Avoid bright light early (wear sunglasses, keep blinds closed).
- Evening at destination: Stay in bright light as late as possible.
- On arrival: Stay up until a reasonable local bedtime, even if you’re tired earlier.
For short trips of one to two time zones, most people adjust naturally without much intervention. These strategies become increasingly important once you’re crossing three or more zones, and they’re essential for long-haul flights of eight or more hours where the time gap is large enough to cause several days of disruption.