You land in a new time zone, and your body is still living in the old one. You're awake at 3 a.m. local time, starving at odd hours, and your brain feels like it's wrapped in cotton. The question everyone asks is simple: how long does jet lag last? The honest answer is that it depends, but there's a general rule you can count on. Most people recover one day per time zone crossed. If you flew from New York to London, that's five hours of difference, so expect about five days of fuzzy sleep and low energy. A trip from Los Angeles to Tokyo, which is eight or nine hours ahead, might take over a week. That rule holds up well for most travelers, but your personal experience might be shorter or longer depending on a few things I'll get into below.
Your body's internal clock, the circadian rhythm, runs on a roughly 24-hour loop. It uses light, meals, and activity to stay synced with your environment. When you cross time zones quickly, your internal clock still thinks it's home. It doesn't reset instantly. It shifts gradually, about one to one and a half hours per day. That's why jet lag isn't just one bad night. It's a slow crawl back to normal. If you want to see how your specific trip will play out, I'd suggest using a jet lag calculator before you book. It can map out your likely adjustment window and help you plan light exposure for the first few days.
Why some people recover faster than others
Age matters. Older adults often take longer to shift their circadian rhythm than younger people. Direction matters too. Flying east is usually harder than flying west. When you fly west, you're extending your day, which is easier for most bodies to handle. Flying east forces you to go to bed earlier than your clock wants, and that's a tougher sell. I've flown both ways many times, and I can tell you from personal experience: the red-eye from the U.S. to Europe always hits me harder than the return trip home.
Your own sleep habits play a role as well. If you already run on a irregular schedule, jet lag can hit you harder. That's because your circadian rhythm is less anchored. A stable routine before you travel gives you a stronger baseline. Even your chronotype matters. Night owls tend to adjust better to westward travel, while morning larks handle eastward flights more smoothly. That's not a hard rule, but it's a pattern I've noticed in myself and in friends who travel a lot.
One thing that surprises many people is that jet lag doesn't always show up right away. Sometimes the first day feels okay because you're running on adrenaline. The second or third day is when the fog settles in. I remember a trip to Singapore where I felt fine for the first 24 hours, then crashed so hard I fell asleep in a food court at 5 p.m. Don't be fooled by an initial burst of energy. Plan for the worst of it to hit around day two or three.
How to shorten the misery
The fastest way to reset your internal clock is light. Bright light in the morning pushes your clock earlier, which helps after flying east. Bright light in the evening pushes it later, which helps after flying west. Get outside and expose your eyes to natural sunlight at the right times. Even a cloudy day provides more light than a hotel room. If you're stuck indoors, a light box can work, but daylight is best.
Melatonin is another tool, but timing is everything. Taking it too early can make you groggy. Too late can shift your clock the wrong way. I take a low dose, 0.5 mg, about three hours before my target bedtime in the new time zone. That's not medical advice, just what works for me. You should talk to your doctor before trying it, especially if you take other medications.
Meals also matter. Your digestive system has its own clock, and eating at local meal times helps signal to your body that the day has shifted. Try to eat breakfast when the locals eat breakfast, even if you're not hungry. It feels forced at first, but it works.
If you want a more precise plan, our free sleep tools include a jet lag planner that factors in your flight direction and arrival time. I use it every time I cross more than three time zones. It takes the guesswork out of when to seek light and when to avoid it.
When jet lag lasts longer than expected
Most people recover within a week or two, even after a big trip. But if you're still feeling off after two weeks, something else might be going on. Travel fatigue, dehydration, and the stress of being away from home can all mimic jet lag. So can poor sleep habits that you picked up during the trip, like staying up late or napping too long. If you're still struggling after two weeks, it's worth checking in with a doctor. They can rule out other issues like anemia or thyroid problems.
One thing I've learned the hard way is that alcohol and caffeine make jet lag worse. I used to think a glass of wine on the plane would help me sleep. It didn't. It fragmented my sleep and left me more dehydrated. Caffeine is useful in the morning, but I cut it off by noon local time for the first few days. That's a small sacrifice for a faster reset.
If you're a frequent traveler, you might also be carrying sleep debt from previous trips. That can make jet lag feel more intense. You can use a sleep cycle calculator to plan your sleep windows in the new time zone, so you're not oversleeping or undersleeping. And if you're tempted to take a long nap on day one, set an alarm for 30 minutes max. Anything longer will steal sleep from the next night.
I also recommend checking out the nap calculator on our site. It helps you time a short nap so you don't wake up feeling worse than before. A 20-minute nap at the right time can be a lifesaver during the adjustment period. But a 90-minute nap at the wrong time can throw off your whole schedule.
Finally, don't forget about caffeine. Its half-life is about five to six hours, which means that 4 p.m. espresso is still in your system at 10 p.m. If you want to know exactly when to stop drinking coffee, use our caffeine half-life tool. I did this on my last trip and realized I'd been sabotaging myself with a late afternoon latte.
Jet lag is temporary, but it doesn't have to ruin your first few days of vacation or your first week at a new job. Give yourself permission to feel sluggish. Keep your expectations realistic. And remember that your body is doing a lot of work to catch up. Be patient with it.
I still remember the first time I flew to Australia. I was off for ten days, and I thought something was wrong with me. It wasn't. I just needed to trust the process. Now I plan for the worst, use the right tools, and I'm back on schedule in half the time. That's the difference between dreading jet lag and just dealing with it.