How long does jet lag last — and how to cut it short

Jet lag usually lasts about one day per time zone crossed — cross five, expect roughly five days. Eastward flights tend to run slower than that, westward flights faster. The rough edges fade well before your body clock has finished moving.

How long does jet lag last, zone by zone

The working rule: your circadian clock shifts roughly an hour a day heading east and somewhat faster — call it an hour and a half — heading west. Divide the zones you crossed by that rate.

Time zones crossed	Flying west	Flying east
2–3	1–2 days	2–3 days
5–6	3–4 days	5–6 days
8–9	5–6 days	7–9 days
11–12	7–8 days	Unpredictable; the clock may shift the "wrong" way

Two caveats. "Recovered" means your clock has realigned, not that you feel fine — most people are functional after two or three days even on a big shift, because sleep debt clears faster than the clock does. And none of it applies to north–south routes: a roughly ten-hour flight from New York to Santiago crosses about one zone and produces travel fatigue, not jet lag. Age and how much daylight you get on arrival move the number too, so treat the table as a planning figure.

Why flying east is harder than flying west

Put a person in dim light with no clocks and their circadian rhythm doesn't run at exactly 24 hours. It runs slightly long — a bit over 24 for most people. That drift is why staying up two hours late feels easy and going to bed two hours early feels impossible.

Flying west asks your clock to do what it already wants to do: delay. The day stretches, local bedtime arrives later in body time, and the drift works with you. Flying east asks for a phase advance, so you're pushing against that drift the whole way. Same six zones, very different week.

Past roughly ten zones east, the advance required is so large that the clock sometimes re-entrains the long way around — delaying instead of advancing — and which way it goes is hard to predict. The circadian rhythm explainer covers the underlying machinery.

Jet lag symptoms, and what's only travel fatigue

Jet lag symptoms cluster around one thing: internal time disagreeing with local time.

• Trouble falling asleep at the local bedtime (typical going east) or waking at 3–4 a.m. and staying awake (typical going west)
• Daytime sleepiness at a consistent, inconvenient hour
• Slower reactions, foggy concentration, reaching for words
• Appetite at the wrong times; a few days of constipation or loose stools
• Headache, flat mood, a general sense of being off

Travel fatigue looks similar for the first day and comes from the trip itself — dry cabin air, hours of immobility, a 4 a.m. alarm, one short night. It clears after a normal night or two, and you get it on domestic flights too. The tell for jet lag is the schedule: if you're wide awake at a predictable hour that happens to be mid-afternoon back home, that's your clock talking, not the airplane. The sleep-loss part recovers on its own timetable — see sleep debt.

Light therapy for jet lag: the lever with real evidence

Light is the dominant input to the circadian system, and timed light is the countermeasure whose mechanism you can actually reason about. The catch: light's effect depends on when it lands relative to your body clock, not on local time.

The reference point is your core body temperature minimum, roughly two hours before your habitual wake time. Light in the hours after that minimum pulls your clock earlier; light in the hours before it pushes your clock later. Get the timing backwards and you move the wrong way — which is how people make a long eastward trip worse by dutifully chasing sunrise.

Going east

You want an advance: light after your temperature minimum, dimness before it. In practice, get outside during the destination's morning, keep the evening dim, and go to bed at the local time even without much sleepiness.

The exception matters on long hauls. Cross more than about eight zones east and the destination's early morning still falls before your temperature minimum in body time, so 7 a.m. sunshine delays you instead of advancing you. For the first day or two, wear sunglasses after local sunrise, start real light exposure late morning, then move it earlier each day as your clock catches up.

Going west

You want a delay, the direction your clock prefers anyway. Take light in the local late afternoon and evening, and stay up until the local bedtime rather than collapsing at 7 p.m. When you wake at 3 a.m. — and westbound you probably will for a few nights — keep the room dark.

Either direction, get the light outdoors: ordinary room lighting is a small fraction of what even an overcast morning delivers.

How to avoid jet lag before you leave

The highest-leverage move happens before departure. Shift your bedtime and wake time by 30 to 60 minutes a day in the direction of travel for two or three days — earlier going east, later going west — and anchor each shifted morning with light at the new wake time. Three days buys 1.5 to 3 hours, which turns a six-hour advance into a manageable three.

The failure mode is remembering the night before and trying to move three hours at once, which is just a short night with extra steps. Half an hour a night is small enough that you'll actually do it, and it's the kind of nudge Bedtime Reminder, a bedtime reminder app for iPhone, is meant to schedule so you're not recomputing the target every evening.

The mechanics are identical to any deliberate schedule move; shifting your sleep schedule earlier covers the pacing and where people stall.

What barely moves the needle

• Setting your watch to destination time at takeoff. Useful for planning. Does nothing to your clock.
• Sleeping on the plane whenever you feel like it. Plane sleep pays off only when it falls inside the destination's night; otherwise it spends the sleep pressure you need for your first real night.
• Alcohol. Sedating for an hour, then it fragments the second half of the night — the half you're already losing.
• Long arrival naps. A two-hour nap at 6 p.m. costs you the night.
• Elaborate fasting protocols. Meal timing influences peripheral clocks, but the case here is much weaker than the case for light.

Melatonin is the other countermeasure studied seriously for travel; timing seems to matter more than amount, and it's worth raising with a clinician.

FAQ

How long does it take to get over jet lag after a 10-hour flight?

Flight duration doesn't set the answer; zones crossed do. A 10-hour flight covering seven zones eastward takes roughly a week for the clock to fully realign, though most people feel workable by day two or three.

Is jet lag worse going east or west?

East, for nearly everyone. Eastward travel demands a phase advance, and the clock's natural period runs slightly longer than 24 hours, so you're working against it. Expect an extra day or two versus the same shift westward.

How to beat jet lag on a two-day trip?

Don't adapt. Under about three days, keep meals and sleep as close to home time as the schedule allows and avoid bright light at the hours that would drag your clock across. Adapting and then re-adapting costs more than staying put.

Do naps help jet lag or make it worse?

Short naps help, long ones hurt. Twenty to thirty minutes before mid-afternoon local time takes the edge off without draining the sleep pressure you need at bedtime.

Can you get jet lag without crossing time zones?

No, though you can feel just as rough. Overnight flights, a truncated night, and hours of sitting still produce travel fatigue that mimics day one. The difference shows up on day two: travel fatigue is mostly gone, while a real phase mismatch keeps waking you at the same wrong hour.