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Free jet lag calculator: enter departure and arrival timezones, flight duration, and departure time. Get time zone difference, local arrival time, severity (minimal → severe), recovery days, and sleep, meal, and light strategies—with numbers for routes like NYC → London and LA → Tokyo.
Last updated: May 25, 2026
Planning sleep at one city? Sleep cycle calculator
Include layovers in total block time
Time difference
5 hours ahead (destination vs departure)
Eastbound (advance sleep — typically harder)
Land (local)
10:30 PM
Arrival date
June 15
Severity: Moderate
Recovery: 3–5 days (often 3–6 days)
Pre-travel shift: ~1.3 h/day for 4 days
Sleep
Pre-shift 1.3 h/day for 4 days. After landing, push to local bedtime even if tired (short nap OK before 3 PM).
Meals
No large meals on the plane after the first half; breakfast at local time day 1 regardless of hunger.
Light
Bright morning light at destination; avoid evening screens first 2 nights.
5 h
5 hours ahead (destination vs departure)
Moderate
Recovery 3–5 days
10:30 PM
June 15, 2026
| Route | Zones | Direction | Severity | Recovery | Land (local) |
|---|---|---|---|---|---|
| New York → London | 5 h | east | Moderate | 3–6 d | 10:30 PM |
| New York → Los Angeles | 3 h | west | Mild | 1–3 d | 11:00 AM |
| Los Angeles → Tokyo | 17 h | east | Severe | 9–19 d | 4:00 PM |
| London → Dubai | 4 h | east | Mild | 2–5 d | 8:00 PM |
| Sydney → Los Angeles | 18 h | west | Severe | 6–13 d | 5:00 AM |
| Time zones crossed | Severity | Typical recovery |
|---|---|---|
| 0–2 h | Minimal | 0–1 day |
| 3–4 h | Mild | 1–2 days |
| 5–8 h | Moderate | 3–5 days |
| 9+ h | Severe | 5–7+ days |
Common planning heuristic: about 1 day of adjustment per time zone when flying east; often somewhat faster when flying west because delaying sleep is easier than advancing it.
zone_diff = arrival_UTC_offset − departure_UTC_offset
arrival_local = departure_local − dep_offset + flight_hours + arr_offset
severity = f(|zone_diff|); eastbound often needs more recovery days
Jet lag is circadian misalignment after rapid timezone change. Our sleep cycle calculator helps bedtime math at one location; this tool handles the shift between cities.
Suggested hashtags: #JetLag #Travel #TimeZone #Sleep #Calculator