I flew from Chicago to Tokyo last spring. Thirteen hours of flying, and my body arrived about eleven hours behind. For the first three mornings I woke at 2 a.m. convinced it was lunchtime. That trip taught me more about jet lag than any article I had read before, mainly because I finally started counting the days instead of just suffering through them.
So how long does jet lag last? The short answer is roughly one day for every time zone you cross. Fly from New York to London and you are looking at about five days of feeling off. Fly to Sydney and you are in for a longer ride, sometimes close to two weeks if you do nothing to help your clock adjust.
That number is not a rule carved in stone. It is a starting point. Eastward travel tends to hit harder than westward travel because your body clock naturally runs a bit longer than 24 hours, which makes it easier to stay up later than to fall asleep earlier. A quick jet lag calculator can give you a personalized estimate based on your departure time, arrival time, and direction of travel, which beats guessing.
What actually determines how long jet lag lasts
Three things matter most: the number of time zones crossed, the direction you fly, and how much you fight your new schedule once you land.
Crossing one or two zones barely registers for most people. Three to five zones is noticeable. Six or more and you are rewriting your internal clock, which takes real time. The direction piece is where things get interesting. Westward trips (New York to Los Angeles) usually resolve faster because you are extending your day. Eastward trips (Los Angeles to New York) require you to fall asleep earlier than your body wants, and that is the hard part.
Then there is behavior. If you land in Paris and immediately stay up until 3 a.m. local time because it feels like dinner back home, you are adding days to your recovery. If you force yourself onto local time from the first meal, you cut the timeline down.
Why your sleep cycle makes this worse
Your circadian rhythm controls more than sleepiness. It regulates body temperature, digestion, hormone release, and alertness. When you cross time zones, that rhythm stays anchored to your home schedule. Your sleep cycle calculator can show you when your natural sleep windows fall, which helps you plan light exposure and naps around your body's actual clock rather than the one on the wall.
Light is the strongest signal for resetting that clock. Morning light in your new location pushes your rhythm earlier. Evening light pushes it later. If you are flying east, get outside in the morning and avoid bright screens late at night. If you are flying west, do the opposite: seek evening light and keep mornings dim.
A realistic day-by-day timeline
Here is what recovery usually looks like for a six to eight zone trip, assuming you make some effort:
- Day 1: You are exhausted but wired. Sleep is fragmented. Do not expect much.
- Day 2 to 3: The worst stretch. You wake too early or crash too early. Appetite is off.
- Day 4 to 5: Sleep starts consolidating. You feel human by mid-morning.
- Day 6 to 8: Mostly adjusted. Minor grogginess in the evening.
For a shorter trip, say three zones, you can compress that into two or three days. For a trip to the other side of the world, tack on another week.
What I do to shorten it
I start shifting my bedtime about 30 to 45 minutes earlier or later each night, beginning three days before I fly. It is not glamorous, but it works. I also set my watch to the destination time the moment I board the plane, and I eat and sleep according to that schedule even if it feels absurd.
Naps help, but keep them short. A 20 to 30 minute nap in the early afternoon can take the edge off without wrecking your nighttime sleep. If you want to plan one properly, a nap calculator is useful for figuring out the right duration and timing so you do not wake up groggier than before.
Caffeine is a tool, not a crutch. I use it in the morning on arrival day and then stop by early afternoon. Knowing your personal cutoff matters because caffeine hangs around in your system longer than most people think. A quick check of caffeine half-life can tell you when that 2 p.m. coffee will actually leave your body, which is often closer to midnight than you would like.
Melatonin is worth mentioning, though I am not a doctor and you should talk to yours. A small dose (0.5 to 1 mg) taken at the right local time can help shift your rhythm. Timing matters more than dose. Take it too early or too late and you push your clock the wrong way.
One more thing: hydration. I used to drink nothing but coffee and wine on long flights and then wonder why I felt terrible. Now I drink water constantly and skip alcohol. The difference is not subtle.
When it is not jet lag
If you are still waking at 3 a.m. two weeks after a trip, something else may be going on. Travel fatigue, dehydration, and plain old stress can mimic jet lag. So can a disrupted sleep schedule you brought home with you. If you want to rebuild a normal routine, our free sleep tools can help you map out a realistic bedtime and wake time instead of trying to fix everything at once.
I keep a note on my phone from that Tokyo trip: "Day 5 finally slept until 6 a.m." It was not a magic fix. It was just time, light, and a little planning. The next time I fly east, I will start shifting three days out and skip the airport wine. That alone should buy me a day.