A jet lag planner built on how the body clock actually shifts
Jet lag is not tiredness from the flight — it is your internal clock still running on home time while the sun, meals and meetings run on local time. The clock resets by roughly an hour a day on its own, which is why a 10-hour change can spoil a week. This jet lag planner speeds that up. Tell it your home and destination time zones, your flight dates, your usual sleep times and whether you are a morning or evening person, and it produces a day-by-day schedule: when to sleep, when to seek bright light, when to avoid it (sunglasses count), when to stop drinking coffee and, for eastward trips, when low-dose melatonin is usually timed.
The plan follows the light-timing rules used in circadian research: light after your body’s temperature low point shifts the clock earlier (flying east), light before it shifts the clock later (flying west). It also picks the faster direction — a 10½-hour New York to Delhi trip is usually quicker to adjust to by delaying the clock 13½ hours than by advancing it.
How to use the Jet Lag Planner
- Pick your home and destination time zones (the list is your browser’s full IANA zone list, so daylight saving is handled automatically).
- Enter the departure date and the arrival date in destination time, and your usual bedtime and wake time at home.
- Choose your chronotype and how many days before the flight you will start shifting (0–3); two days of pre-adjustment saves about two days of jet lag.
- Read the headline — the time difference, the shift direction and the number of days to adjust — then the table: sleep window, seek-light window and avoid-light window for each day, in the local time of wherever you are.
- Press Print plan for a one-page sheet to keep in your bag, or Copy plan as text to paste into your notes or calendar.
Jet Lag Planner features
Direction chosen for you
Compares an advance (east) and a delay (west) using chronotype-specific rates — about 1 h/day advancing, 1.5 h/day delaying — and picks the faster route to the local clock.
Light windows that follow the shift
Seek and avoid windows are anchored to your core body temperature minimum (about 2.5 h before wake) and move day by day as the clock shifts.
Pre-flight adjustment
Start shifting one to three days before departure, when it is easiest, and arrive with part of the work already done.
Caffeine and melatonin timing
A cut-off for caffeine eight hours before target bedtime, and a melatonin note timed five hours before the target bedtime on eastward trips, labelled as general guidance.
Printable and copyable
A clean print layout and a plain-text version for notes.
East versus west: why the direction matters
The body clock runs slightly longer than 24 hours, so delaying it (staying up later) is easier than advancing it. Flying west asks for a delay and most people manage about 1.5 hours a day; flying east asks for an advance at closer to 1 hour a day. That is why Europe-to-India feels harder than the return, and why morning people (who advance more easily) and night owls (who delay more easily) get different rates.
For very large eastward changes — roughly 9 hours or more — delaying the clock “the long way round” can be faster than advancing it. The planner compares both and reports the one with fewer days; you can see the alternative by switching chronotype or flipping origin and destination.
How the light rules work
Bright light is the strongest signal the clock receives. Its effect depends on when it arrives relative to the core body temperature minimum (CBTmin), which for a 23:00–07:00 sleeper falls around 04:30:
- “Bright light” means daylight or a 10,000-lux light box; ordinary room light is weak but phone and laptop screens at night still count against you.
- Avoiding light does not mean staying indoors — dark sunglasses in the avoid window are enough.
| You want to… | Seek bright light | Avoid bright light | Typical trip |
|---|---|---|---|
| Advance the clock (sleep earlier) | About 3 hours after CBTmin — in practice straight after waking | The 4 hours before CBTmin — the evening and early night | Flying east: London → Delhi, Delhi → Tokyo, New York → Paris |
| Delay the clock (sleep later) | The 5 hours before CBTmin — the evening and late night | The 3 hours after CBTmin — the early morning | Flying west: Delhi → London, Paris → New York, and very long eastward hops |
Worked example: New York to Delhi in November
New York is UTC−5 in November and Delhi UTC+5:30: a 10 h 30 min jump. Advancing 10.5 hours at 1 h/day takes 10½ days; delaying 13.5 hours at 1.5 h/day takes 9, so the planner delays. You stay up 1½ hours later on the two nights before the flight, and on arrival sleep from about 14:00 to 22:00 local, seeking afternoon light and wearing sunglasses after 19:30. Each day the window slides 1½ hours later until it reaches 23:00–07:00. Check connections with the Layover Calculator and clocks with the Time Zone Converter.
Jet Lag Planner FAQ
How many days does it take to get over jet lag?
Unaided, about one day per hour of time difference eastward and a little less westward. With timed light and sleep as in this planner, most people adjust in roughly half that: a 5½-hour Delhi–London change in about 4 days, a 10½-hour New York–Delhi change in about 9.
Should I start adjusting before I fly?
If you can, yes. Shifting sleep by an hour or so a day for two or three days before departure, with light at the right times, means you land partly adjusted. The planner builds those days into the table.
Is this jet lag planner medical advice?
No. It applies published circadian light-timing rules and general sleep-hygiene guidance. If you take medication, are pregnant, or have a sleep, heart or mood condition, ask a doctor or pharmacist before using melatonin or changing your sleep pattern.
When should I take melatonin for jet lag?
Guidelines most often suggest a low dose about five hours before the target bedtime on eastward trips, for the first few days. It is of little help for westward delays. The planner shows the local time this corresponds to on each day; discuss suitability with a pharmacist.
Does the planner account for daylight saving time?
Yes. Offsets are taken from your browser’s time-zone database for the actual dates, so a November New York departure uses EST and a July one uses EDT.