The general rule
The most widely cited rule of thumb is that jet lag takes roughly one day per time zone crossed to resolve. Fly across five zones, expect about five days to feel fully normal.
This is a reasonable starting point, but it oversimplifies things. The real answer depends on how many zones you crossed, which direction you flew, and what you do (or don't do) to manage it.
Direction makes a big difference
Flying east takes longer to recover from than flying west. Your body's internal clock runs slightly longer than 24 hours, so it's easier to delay (stay up later) than to advance (go to bed earlier).
Westbound recovery runs at about 0.5 to 1 day per timezone crossed. Five zones west means 3 to 4 days.
Eastbound recovery runs at about 1 to 1.5 days per timezone crossed. Five zones east means 5 to 7 days.
A London to New York trip (five zones west) and a New York to London trip (five zones east) have measurably different recovery periods, even though the journey is identical.
What "recovery" actually means
Full circadian alignment, where your body temperature rhythm, melatonin rhythm, and sleep-wake cycle are all synchronised with local time, takes the longest. But you'll feel functionally normal well before that.
Most travellers go through three phases. Days one and two are the worst: sleep is fragmented, energy is unpredictable, appetite is off, concentration is poor. Days three to five show noticeable improvement: sleep is longer, more consolidated, and daytime functioning is close to normal. Days five to seven and beyond bring full adjustment: sleep timing matches local time and the background fatigue is gone.
For shorter shifts (2 to 3 zones), many people skip the acute phase entirely and just feel slightly off for a day or two.
What affects your personal recovery time
Older adults generally take longer to adjust. Circadian flexibility declines with age, and melatonin production decreases. A 25-year-old crossing six zones might adjust in four days; a 65-year-old on the same route might need six or seven.
Your chronotype matters too. Morning people tend to adjust faster after eastbound travel. Night owls adjust faster after westbound. Neither has a universal advantage; it depends on the direction.
If you arrive already short on sleep (from pre-trip packing, early airport runs, or poor sleep on the plane), everything takes longer. Sleep debt and jet lag compound each other.
Travellers who actively manage their light exposure, melatonin timing, and sleep schedule adjust measurably faster than those who just try to "push through." The difference can be 1 to 3 days depending on the route.
How to speed things up
The fastest recovery comes from three things working together.
Timed light exposure: morning light after eastbound travel, afternoon and evening light after westbound. This is the single most effective tool.
Low-dose melatonin (0.5 to 1mg) at destination bedtime for the first 3 to 5 nights.
A consistent wake time: get up at the same local time every morning, regardless of how you slept. This anchors your clock.
With all three in place, you can often cut a day or two off the standard recovery time.
When it takes longer than expected
If you're still feeling significantly off after 7 to 10 days, something else might be going on. Persistent fatigue after travel can be caused by accumulated sleep debt (not jet lag itself), illness picked up during travel, dehydration, or underlying sleep issues that travel has surfaced.
If symptoms persist beyond two weeks, it's worth talking to a GP.