Scientists understand jet lag well, yet most of us still fight it with old habits: stay awake the whole flight, drink coffee all day, push through and hope. None of that deals with the real problem, a body clock that is still running on home time. Reset that clock, rather than just battling tiredness, and you can feel normal by day two instead of dragging yourself around on day five.

Below I explain what jet lag is, why some routes and some people suffer more, and the research-backed habits that shorten recovery: timing your light exposure, using melatonin properly, and shifting your sleep before you fly, which is easier than it sounds.

What Jet Lag Is

Jet lag happens when your circadian rhythm, the internal 24-hour clock that controls sleep, alertness, hormones, digestion and body temperature, falls out of step with day and night at your destination. The master clock is a small cluster of nerve cells in the brain called the suprachiasmatic nucleus. It takes its main cue from light reaching your eyes, and weaker cues from when you eat, move and socialize.

The clock doesn't reset instantly. Left alone, it shifts by roughly one hour per day for eastward travel and slightly faster, around 1 to 1.5 hours per day, for westward travel. Cross five time zones, do nothing, and it can take four or five days before your body fully settles into the new time. This guide is about shrinking that.

Two things are worth knowing. First, flying east, say from New York to London, is usually harder than flying west across the same number of time zones. Going east means falling asleep earlier than your body wants, and most people find that much harder than staying up late. Second, how bad jet lag gets depends on the number of time zones you cross, not how long you're in the air. An 11-hour flight from London to Johannesburg crosses only one or two time zones and causes little jet lag, while a 7-hour flight from New York to London crosses five.

The Pre-Flight Shift Protocol

One of the most effective things you can do happens before you board, and few people bother because it means adjusting your sleep for a few days at home. The idea is simple: two or three days before you leave, start moving your bedtime and wake-up time toward your destination's schedule.

For eastward travel (shifting your schedule earlier), go to bed 30 to 60 minutes earlier each night for two to three nights before you fly, and get bright light exposure in the morning as soon as you wake up, outdoor light if possible, or a light therapy device if it's dark outside at your wake time. For westward travel (shifting later), stay up 30 to 60 minutes later each night and seek bright light in the evening instead of the morning.

Even shifting 1.5 to 2 hours over three days leaves your body less to catch up on when you land. It won't stop jet lag on a long trip across many zones, but it can take a day or so off recovery. Studies at Rush University Medical Center in Chicago found that gradually moving sleep earlier, combined with bright morning light, shifted people's body clocks before they even left home.

Light: Your Most Powerful Tool

Light affects your body clock more than anything else, including melatonin, caffeine or sleep timing on their own. Getting light at the right times, and avoiding it at the wrong ones, does more to reset your clock than almost anything else here.

The basic rule is to get bright light when it pushes your clock in the direction you need, and to avoid it, with sunglasses, an eye mask or dim rooms, when it would push the wrong way. After flying east, that usually means morning light at your destination and less light in the evening for the first few days. After flying west, it's roughly the opposite. Evening light helps, and dodging very early morning light for a day or two stops you waking too soon.

The exact best times depend on your route, which is why jet lag planning apps are worth a look. The Timeshifter app, built with input from sleep scientists, generates a personalized light-avoidance and light-seeking schedule based on your specific flight itinerary, chronotype, and usual sleep habits. It's one of the few paid travel apps I'd recommend if you take more than a couple of long-haul trips across many time zones each year.

Melatonin: What It Does and How to Use It Correctly

Melatonin is a hormone your brain releases when it gets dark, telling your body it's time for sleep. Taken as a supplement at the right time, it can help nudge your body clock and make it easier to fall asleep earlier than feels natural. Taken at the wrong time, or in a big dose, it does little and can leave you groggy the next day.

After flying east, studies support a low dose, about 0.5mg to 3mg, taken close to your planned bedtime in the new time zone for three to five nights, starting on travel day or the day after you arrive. Larger doses don't work better and are more likely to leave you groggy. For westward travel, melatonin is generally less necessary since falling asleep later comes more naturally, though a small evening dose in the first couple of days can still help consolidate sleep.

In the US, melatonin is sold over the counter, often as 5mg or 10mg tablets, far more than you need to shift your body clock. In the UK it's prescription-only, and rules differ across the EU and elsewhere, so check the law in both your home country and your destination before you pack any. For most healthy adults it isn't habit-forming at these doses, but speak to a doctor or pharmacist first if you take other medicines, especially blood thinners, drugs that affect the immune system, or other sleep aids, or if you are pregnant.

What to Do During the Flight

Use the flight to get a head start, not just to survive it. As soon as you board, switch your mind to destination time and try to do what you'd normally be doing at that hour there.

If it's nighttime at your destination for most of the flight, that's your cue to sleep: use an eye mask, noise-canceling headphones, and skip the alcohol, which fragments sleep quality even though it can help you fall asleep initially. If it's daytime at your destination, stay awake, keep your window shade up if you can, and don't nod off just because the cabin is dark and you're bored.

Drink more than you think you need. Cabin air is very dry, often around 10 to 20% humidity, and dehydration makes you more tired and foggy on top of the jet lag. A rough target is a cup of water (about 250ml) every hour. Alcohol and lots of coffee make it worse.

Time Zones Crossed	Direction	Typical Full Recovery
1 to 3	Either	1 to 2 days
4 to 6	Westward	2 to 4 days
4 to 6	Eastward	3 to 5 days
7 to 10	Westward	4 to 6 days
7 to 10	Eastward	5 to 8 days

The First 48 Hours After Landing

What you do on arrival day matters a lot. After a long flight you'll want to collapse into bed whatever the local time. It feels great, but if it's daytime, it can set you back a day or more.

If you land in the morning or early afternoon, stay awake until a normal local bedtime (9 or 10 PM is fine) and get outside into daylight. If you really can't cope, take a nap of 20 to 30 minutes with an alarm set. Any longer and you risk falling into deep sleep, and waking from that leaves you groggier than no nap at all.

Meal timing at your destination also sends a circadian signal, separate from light. Eat your first proper meal at a normal local mealtime, even if you aren't hungry, to reinforce the new schedule. Some sleep researchers suggest a good breakfast at local morning time as a useful extra cue, especially after flying east.

Caffeine, Exercise, and Other Tools

Caffeine won't reset your body clock the way light does, but used carefully it helps you stay alert while you adjust. Have a coffee to get through the first afternoon, but stop 6 to 8 hours before your new bedtime. Caffeine takes around five hours for your body to clear half of it, so an afternoon coffee can still be working when you try to sleep.

Gentle exercise, ideally outdoors, on arrival day and the next day or two seems to help a little, probably because you get daylight, warm up and stay alert. It doesn't have to be a workout. A 20 to 30 minute walk in daylight does most of the job, and it beats sitting in your hotel room on that first foggy afternoon.

Some travelers fast for 12 to 16 hours before eating breakfast at local time on arrival. The idea comes partly from research at Harvard, done in mice, suggesting the body has a "food clock" separate from the light-driven master clock. The evidence in people is weaker than for light and sleep timing, and fasting isn't suitable for everyone, including people with diabetes. It's worth knowing about, but don't rely on it.

Jet Lag in Children and Older Travelers

Children often adjust faster than adults, but the days in between can be rough: meltdowns, odd appetites and sleepy afternoons that can derail the first day or two. The same light-exposure principles apply: get kids outside during destination daytime, resist the urge to let them nap for hours during the day even if they're exhausted, and hold meal times to the new schedule as closely as practical.

Older travelers, especially over 60, often adjust more slowly and feel more tired during the day while they do, partly because body clocks change with age and sleep tends to be lighter. The same approach works, but leave a spare day or two before anything demanding, such as a big hike, an important meeting or a long onward trip.

Choosing Flights and Layovers to Minimize Jet Lag

You can start fighting jet lag when you book, because some routes and flight times are easier on your body than others. Going east on a long flight, an overnight flight that lands in the morning fits naturally with the sleep-then-wake pattern you need.

Layovers matter too. A short connection of under two hours barely disturbs your routine, but a six-hour wait, especially one that tempts you into a long nap on airport benches, can undo the adjustment you did at home. If you're stuck with a long layover, keep following your destination's clock for light and sleep, and take a walk around the terminal, or outside if your visa allows, rather than sitting still.

If you have a choice, breaking a very long trip with a night's stopover can sometimes leave you less wrecked than one huge nonstop flight across many time zones, especially if you're older or struggle with jet lag. That isn't always true, since a nonstop means less total travel time and hassle, but it's worth considering if long nonstops have floored you before.

Jet Lag Myths That Don't Hold Up

Plenty of popular jet lag advice does little, and some of it makes things worse.

"Just stay awake the whole flight and push through until local bedtime." This works reasonably well for short shifts of a few time zones but becomes counterproductive on long eastward hauls crossing six or more zones, where the sleep deprivation itself becomes a bigger problem than the circadian misalignment, and the resulting exhaustion often triggers exactly the kind of uncontrolled, badly timed daytime sleep that resets recovery further back.

"Compression socks and hydration prevent jet lag." Compression socks lower the risk of blood clots on long flights, which is worth taking seriously, but they do nothing for your body clock. Hydration helps with general flight fatigue and cognitive fog, which overlaps with how jet lag feels, but it doesn't reset your internal clock on its own.

"Jet lag pills and specialty supplements beyond melatonin are worth the money." Most "jet lag relief" products mix melatonin with vitamins and herbal extracts, and there's little evidence they do more than melatonin alone. Where melatonin is legal for you, a correctly timed low dose does the same job for far less money.

"There's nothing you can do, just wait it out." This is the most common belief and the most costly, given how much we now know about light timing, shifting sleep before a flight and melatonin. Waiting it out is fine for a short trip if the effort doesn't seem worth it, but it's a choice, not something you're stuck with.

A Worked Example: New York to London

Here's how it looks on a real route: New York to London, five hours east, on an overnight flight that lands early in the morning.

Three days before departure: Shift bedtime and wake time about 30 minutes earlier than usual, with bright light immediately on waking. Two days before: Shift another 30 minutes earlier, same light exposure. One day before: Final 30 to 45 minute shift, packing done early so the evening stays calm and consistent with the earlier bedtime.

On the flight: You leave in the evening New York time, which is already around midnight in London, so try to sleep as soon as the meal is cleared. Wear an eye mask and skip the wine. Wake an hour or so before landing and open the window shade to catch the morning light.

Day one in London: Land around 7 AM local time having gotten some sleep on the plane. Skip the early check-in nap. Get outside for an hour or more of walking in daylight during the morning, eat a proper breakfast at a normal London time, and keep busy with gentle activity all day. If you really need it, take one 20-minute nap in the early afternoon with an alarm, and nothing after 3 PM. If melatonin is suitable for you, take 0.5mg to 1mg about 30 to 60 minutes before going to bed at 9:30 or 10 PM.

Days two and three: Continue the same pattern, outdoor light in the morning, normal local mealtimes, melatonin at bedtime if sleep is still fragmented, avoiding caffeine after early afternoon. Many people who do this feel close to normal by day two or three, rather than day four or five.

Does All This Make a Difference?

Put together, shifting your sleep before you fly, getting light at the right times, taking low-dose melatonin at the right time and behaving sensibly on arrival can shorten recovery noticeably. Frequent long-haul travelers who adopt these habits often say crossing time zones feels completely different. It isn't magic, and an 8-time-zone flight east will still cost you something. But doing the basics well can mean feeling human by day two instead of foggy on day five, and on a short holiday that's the difference between enjoying the first half and losing it.

You don't need expensive gear or a complicated plan. A light therapy lamp helps if you fly long-haul often, but daylight and a planned sleep schedule do most of the work for free. What you do need is discipline in the first 48 hours, which is exactly when a bed at the wrong time of day is hardest to resist.

For a short trip across two or three time zones, don't overthink it. A slightly off day is a fair price and the full routine is overkill. Save the effort for long-haul trips across many zones, business trips with meetings on the first morning, or any trip where the first two days really count. Treat jet lag as a problem you can plan for, not something you just have to put up with, and you'll notice the difference on your very next trip.