Jet Lag Recovery Calculator
Estimate recovery days after crossing time zones. Choose departure and arrival zones. View direction, zones crossed, and a recovery timeline.
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Helping Notes
Pick departure and arrival zones; direction and zones crossed are computed automatically from current offsets.
Eastward usually requires more days than westward. Actual recovery varies with sleep schedule and light exposure.
Results
Estimated Recovery Time
Direction
Time Zones Crossed
What Is a Jet Lag Recovery Calculator?
A Jet Lag Recovery Calculator estimates how many days you’ll need to realign your body clock after crossing time zones, then generates an actionable schedule for sleep, light exposure, caffeine, and optional melatonin timing. By combining your home and destination time zones, flight timing, usual sleep window, and flexibility for pre‑trip shifting, the tool outputs a simple day‑by‑day plan. It also adapts to direction of travel: eastbound trips typically require phase advances (earlier sleep/wake), while westbound trips favor phase delays (later sleep/wake). The goal is not medical treatment but fast, practical guidance for minimizing fatigue, grogginess, and performance dips during and after travel.
About the Jet Lag Recovery Calculator
The calculator models circadian adjustment as a daily phase shift with typical limits (about 1–1.5 hours/day east, 1.5–2 hours/day west). It estimates recovery days from the absolute time‑zone gap, then allocates light and sleep windows to hit the target at an achievable pace. Morning bright light advances your clock; evening bright light delays it. Likewise, brief low‑dose melatonin early in the local night can aid eastward advances, while strict evening light avoidance helps when advancing. The plan accounts for preflight shifting (if you start moving your bedtime before departure) and respects your preferred sleep length so you don’t under‑sleep during transition. Outputs include recovery days, recommended exposure times, bedtime/wake targets, and gentle nap rules to avoid fragmenting nighttime sleep.
Time‑zone gap: ΔTZ = |TZdest − TZhome|
Daily shift capacity: Reast ∈ [1, 1.5] h/day; Rwest ∈ [1.5, 2] h/day
Estimated recovery days: D = ⌈(ΔTZ − P)/Rdir⌉+ where P = min(ΔTZ, Rdir × dayspre)
Target bedtime/wake (day k): BTk = BT₀ + k·s; WKk = WK₀ + k·s with s = sign(dir)·min(Rdir, Ruser)
Light exposure window (simplified): East: expose = [WKk, WKk + 2h]; West: expose = [BTk − 2h, BTk]
Melatonin cue (heuristic): tmel = BTk − 3h (east); omit/delay for west
Caffeine cut‑off: tcaf_cut = BTk − 8h
How to Use This Jet Lag Recovery Calculator
- Enter origin and destination time zones, flight date/time, usual bedtime/wake, and how many days you can pre‑shift.
- Choose direction (east/west) and set a comfortable daily shift limit.
- Submit to see recovery days, daily bed/wake targets, light exposure/avoidance windows, caffeine cut‑offs, and optional melatonin cues.
- Follow the schedule, prioritize outdoor light, dim evenings, and keep consistent wake times. Consult a clinician for medication questions.
Examples
- NYC → Paris (ΔTZ = 6 east), no pre‑shift, Reast = 1.5 h/day: D = 4 days. Morning light; melatonin ~3 h before target bedtime.
- LA → Tokyo (ΔTZ = 17 east via Pacific), pre‑shift 2 days @ 1.5 h/day: P = 3 h, D = 10 days.
- London → NYC (ΔTZ = 5 west), Rwest = 2 h/day: D = 3 days. Seek evening light; avoid early‑morning bright light.
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FAQs
How many days does jet lag last?
Typical adjustment is 1–2 hours per day. Divide the time‑zone difference by that rate to estimate recovery days.
Is eastbound travel really harder?
Often yes. Advancing the body clock is slower than delaying, so eastbound trips usually take longer to adjust.
When should I get bright light?
Eastbound: early local morning. Westbound: late afternoon or early evening. Avoid the opposite time to prevent shifting the wrong way.
Should I nap after arrival?
Short, early‑day power naps (10–20 minutes) can help. Avoid long or late naps that disrupt nighttime sleep.
What about melatonin?
Some travelers use it in the early local night for eastbound advances. Discuss use, timing, and dosing with a clinician.
Can I pre‑shift before the flight?
Yes. Move bedtime/wake by 1 hour per day toward destination time to reduce post‑arrival adjustment.
How should I use caffeine?
Use strategically after wake time and stop 6–9 hours before target bedtime to protect sleep.
Does hydration help?
It won’t shift your clock but supports comfort. Drink water regularly and moderate alcohol on long flights.
Do night flights change the plan?
They influence when to sleep on board. Aim for sleep aligned with destination night as much as possible.
What if I must perform immediately?
Use bright light, strategic caffeine, brief naps, and strict wake times. Consider arriving earlier when possible.
Can kids follow the same schedule?
Principles are similar, but schedules must be gentler. Consult pediatric guidance for supplements or medications.
Will wearables help?
Yes. Use them to anchor wake times, track sleep, and prompt light exposure and wind‑down routines.