What does the calculator do?
It works out how far and in which direction each traveler's body clock has to move, then schedules sleep, light, darkness, naps, meals and optional melatonin day by day, from a head start at home until everyone is on local time.
How is the body-clock shift calculated?
- Time difference on your dates. Both time zones are compared for your actual travel dates, so daylight saving time changes and the International Date Line are handled.
- Direction. A shift east means advancing (moving earlier); west means delaying. For eastward shifts of 10 hours or more, the plan delays the long way around (for example, 10 hours east becomes 14 hours later), which is usually faster because body clocks delay more easily. Some researchers suggest switching to delaying from about 8 hours east; we keep the advance up to 9 hours because many families prefer shorter trips with an earlier schedule.
- Speed. We assume clocks advance about 1 hour a day and delay about 1.5 hours a day with good light timing, so estimates are conservative for advances.
- Short trips. For stays of 3 days or less, the plan shifts only part way (up to 3 hours) and keeps you close to home time.
How are light windows chosen?
Each person's body-temperature low point (CBTmin) is estimated as about 2.5 hours before their usual wake time. Light in the 6 hours after CBTmin shifts the clock earlier; light in the 6 hours before it shifts the clock later. The plan tells you when to seek daylight and when to wear sunglasses or stay indoors, and moves those windows each day as your clock shifts.
How are kids handled differently?
- Pre-trip steps of 15 minutes a day (ages 0–3), 30 (4–12), 45 (teens) and 60 (adults).
- Each child's bedtime is calculated from their own home bedtime and never set before you arrive on day 1.
- Naps follow age: toddlers keep naps on local time; older kids and adults get short, early naps only.
- Melatonin guidance for children always says to ask a pediatrician first, and never for babies or toddlers.
What are the limits?
- Body clocks vary. Night owls, early birds and teens can need more or less time.
- Research on jet lag in young children is limited; kid schedules adapt adult research conservatively.
- If no flight times are entered, we assume a typical flight for the route.
- Not medical advice. Talk to your doctor about sleep disorders, pregnancy, medications or health conditions.
Who is behind this site?
Jet Lag With Kids is a free, independent project based in Denver, Colorado, built for parents planning long trips with kids. It is not written by medical professionals and has no medical credentials; every recommendation follows the published sources below. There are no ads or sponsored recommendations. Content was last reviewed Nov 9, 2026.
How is my privacy protected?
Plans are calculated entirely in your browser. Share links contain your inputs in the URL, so only share them with people you trust. We use cookie-free Cloudflare Web Analytics to count visits; no personal data is collected.
Frequently asked questions
Who makes Jet Lag With Kids?
It is a free, independent project based in Denver, Colorado. It is not written by doctors and does not replace medical advice; it turns published circadian research into schedules families can follow.
Why does the calculator sometimes say to avoid morning light?
Light just before your body-temperature low point pushes the clock later, and light just after it pushes the clock earlier. After big eastward flights, early-morning destination time can still fall before your low point, so morning light would push you the wrong way for the first days.
Why do kids get smaller steps?
Children's bedtimes are less flexible and they get overtired quickly, so pre-trip shifts are 15 minutes a day for ages 0–3, 30 minutes for 4–12 and 45 minutes for teens, versus 60 for adults.
Is my data stored?
No. Plans are calculated in your browser and nothing you type is sent to us. We use cookie-free Cloudflare Web Analytics to count page views.
Sources
- CDC Yellow Book 2026: Jet Lag Disorder. US Centers for Disease Control and Prevention guidance for travelers and clinicians.
- Eastman CI, Burgess HJ. How to travel the world without jet lag. Sleep Med Clin, 2009. The light-timing and pre-flight shifting method this calculator follows.
- Burgess HJ et al. Preflight adjustment to eastward travel: 3 days of advancing sleep with and without morning bright light. J Biol Rhythms, 2003. Shifting sleep 1 hour a day before an eastward flight.
- Eastman CI et al. Advancing circadian rhythms before eastward flight: a strategy to prevent or reduce jet lag. Sleep, 2005. How fast body clocks can be moved earlier before travel.
- Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews. Systematic review of melatonin for jet lag in adults.
- American Academy of Sleep Medicine: Melatonin use in children and adolescents (health advisory). Advises involving a health care professional before giving children melatonin.
- American Academy of Pediatrics (HealthyChildren.org): Melatonin and children's sleep. Pediatric guidance on melatonin dose, timing and safety.
How we turn this research into plans: methodology.
Not medical advice. General sleep and travel guidance based on published circadian research. Ask your doctor or pediatrician about melatonin or other supplements, pregnancy, medications or health conditions. Never give melatonin to babies or toddlers.