Jet Lag Calculator: Personalized Time‑Zone Shift Plan

Use the jet lag calculator

Enter your time zones and travel times to build a personalized sleep‑shift and light schedule for faster adjustment.

How to Use Jet Lag Calculator: Personalized Time‑Zone Shift Plan

1. Step 1: Select Time Zones

   Choose your origin and destination time zones, or switch to manual to enter the time difference.

2. Step 2: Add Travel Times

   Enter your departure and arrival dates and local times so the tool can estimate direction and schedule.

3. Step 3: Set Your Sleep

   Add your usual bedtime and wake time to anchor the plan to your real routine.

4. Step 4: Pick Shift Pace

   Adjust how many minutes per day to shift. Eastbound usually advances, westbound delays.

5. Step 5: Review Your Plan

   Read the pre‑trip schedule and the arrival light windows, then follow the day‑by‑day guide.

Key Features

• Travel direction and time‑zone inputs
• Pre‑trip sleep‑shift schedule (30–120 min/day)
• Arrival light exposure and avoidance windows
• Flexible manual time‑difference option with summaries
• Optional melatonin timing note (non‑medical)

Understanding Results

Formula

The planner estimates how many days you need to adjust by dividing the total time‑zone difference by your chosen daily shift pace. Days ≈ ceil(|ΔTZ| ÷ pace). When traveling eastbound, you typically advance bedtime and wake earlier; for westbound trips, you usually delay bedtime and wake later. The schedule shows daily targets so you can step toward the destination time.

Reference Ranges & Interpretation

Many people can advance about 0.5–1 hour per day and delay 1–2 hours per day. Eastbound adjustment is often slower; westbound usually feels easier. For a 6‑hour eastbound trip, a moderate 0.75 h/day advance takes about 8 days; if you can only advance 0.5 h/day, plan for 12 days. If you cannot shift before travel, use the arrival light windows to accelerate the first few days on location.

Assumptions & Limitations

The tool simplifies circadian biology into practical steps. It does not calculate sunrise/sunset or diagnose sleep disorders. Individual responses vary with age, light exposure, social schedule, caffeine, and prior sleep. Treat results as a guide. If jet lag symptoms or daytime sleepiness are severe or persistent, consult a qualified professional. For general travel guidance, see the CDC’s overview on jet lag (external).

Complete Guide: Jet Lag Calculator: Personalized Time‑Zone Shift Plan

Use our jet lag calculator to build a pre‑trip sleep‑shift plan and post‑arrival light schedule. Enter time zones and travel times to get a day‑by‑day guide.

Jet lag happens when your internal clock and the local clock disagree. Bright light, darkness, meal timing, and exercise can nudge that clock earlier or later. The goal is not perfection — it is steady progress that keeps you alert in the daytime and sleepy at night where you land. This guide explains how to use the tool, why eastbound and westbound trips feel different, and how to build a plan that fits real life.

How the jet lag calculator works

The calculator takes four main inputs: your origin and destination time zones (or a manual difference), your departure and arrival times, your usual bedtime/wake time, and the pace at which you want to shift your sleep. From those, it computes the total time‑zone difference, the likely direction of travel (east or west), and a day‑by‑day schedule that moves your sleep toward the destination schedule.

Two pieces make it practical: a pre‑trip plan that nudges your sleep in small steps before you fly, and an arrival plan that focuses on daylight and darkness in the right windows. You can change the shift pace to match your reality. If you have a flexible week before travel, a gentle 30–60 minutes per day may feel easy. If you only have two days, a faster pace can still help — especially for westbound trips, which many people find easier.

There is no single perfect schedule. Instead, the tool gives you a reasonable path to follow. If you miss a day or a step, keep going. Small, consistent changes matter more than one perfect day.

Eastbound vs westbound: which is harder?

Most travelers report that going west feels easier than going east. That is because delaying sleep (staying up later) is more natural for the human clock than advancing it (going to bed earlier). If you have ever stayed up late on a weekend and slept in the next morning, you have felt this effect. The calculator uses faster default pacing for westbound trips and slower pacing for eastbound trips to reflect this asymmetry.

For example, if you fly from New York to London (about 5 hours east), you may advance about 0.5–1.0 hour per day. From Los Angeles to Tokyo (about 16 hours ahead via the date line, effectively 8 hours west), many people can delay 1–2 hours per day. The total time‑zone difference is the same magnitude either way, but the direction changes the pace that feels comfortable.

Use how you feel as your guide. If an early bedtime leaves you wide awake, choose a smaller advance. If staying up late is easy, you can safely pick a slightly faster delay and still wake at a good local hour.

Choosing your shift pace

Shift pace is the number of hours per day you move your sleep. Most people do well with 0.5–1.0 hours/day for eastbound trips and 1.0–2.0 hours/day for westbound trips. The right pace depends on your schedule, your sensitivity to light, and how tired you expect to be on arrival. Faster is not always better — the goal is a schedule you can keep.

Pick your pace in the tool and watch the estimated number of days to adjust. That number is simply the total time‑zone difference divided by your pace, rounded up. If you cannot start early, you can set pre‑trip days to zero and focus on the arrival light windows for the first few days on location.

If you are unsure, start with these defaults and adjust after a day or two:

• Eastbound (advance earlier): 0.75 hours/day to start
• Westbound (delay later): 1.5 hours/day to start
• Short trips (<3 hours): pace matters less; lean on light timing

Pre‑trip schedule examples

Example 1: New York → London (5 hours east). Usual sleep 11:00 pm–7:00 am. Three days before departure, advance by 45 minutes per day. Bedtimes become 10:15 pm, 9:30 pm, and 8:45 pm. Wake times move to 6:15 am, 5:30 am, and 4:45 am. On arrival in London, morning light and a local early bedtime help finish the shift.

Example 2: Los Angeles → Tokyo (8 hours west effective). Usual sleep midnight–8:00 am. Two days before departure, delay by 90 minutes per day. Bedtimes become 1:30 am and 3:00 am; wake times move to 9:30 am and 11:00 am. After arrival, seek late‑afternoon light and avoid bright early mornings. You will often feel aligned much faster going west.

If your schedule is rigid before the trip, shift your meal timing and light exposure instead: dim the last hour before bed, step outside early after waking, and keep caffeine early in the day. Those cues still move your clock in the right direction even if bedtime cannot change much.

Arrival light and darkness strategy

Light is the strongest signal to your internal clock. The calculator summarizes two simple windows that work for most people: when to seek bright light and when to avoid it. Eastbound travelers generally benefit from morning light and reduced evening light. Westbound travelers often use late‑day light and avoid bright early mornings for the first few days. If the weather cooperates, go outdoors during the recommended window — outdoor light is far stronger than indoor light.

At night, make bedrooms dark: close shades, cover bright LEDs, and keep phones face down. If you wake early, stay in low light to prevent your clock from locking onto the wrong time. A short, quiet activity in dim light is better than turning on overhead lighting.

If you land late at night, go to bed as soon as you can and seek light after you wake at a reasonable local hour. If you land early in the morning, try to get morning light and avoid long naps. A short nap (20–30 minutes) in the early afternoon can reduce sleepiness without pushing bedtime later.

Naps, caffeine, and hydration

A short nap early in the afternoon can help you through the first one or two days after a long‑haul flight. Keep it under 30 minutes and avoid late naps that cut into bedtime. If you struggle with middle‑of‑the‑night awakenings, skip naps for a day or two and lean on morning light instead.

Caffeine is fine in the morning and early afternoon, but late‑day coffee can push your clock the wrong way. If you are curious how long caffeine sticks around for you, try the Caffeine Calculator to predict levels near bedtime.

Dehydration makes jet lag feel worse. Use the Hydration Calculator to set a reasonable daily target, and drink a glass of water after every flight segment and each cup of coffee or tea.

Using the tool for real trips

Business travel, short stays (2–3 days): For quick eastbound trips, go light on pre‑trip changes and lean on morning light and early meals on location. For westbound quick trips, delaying bedtime slightly and getting late‑day sun may be enough. If you will return home immediately, consider partial adjustment rather than a full shift.

Family travel, longer stays (1–2 weeks): Use a moderate pace and start 3–5 days before departure if possible. Keep the first evening calm, plan outdoor time after breakfast, and set consistent bedtimes for kids. If you need help picking local sleep times, try the Bedtime Calculator or the Sleep Cycle Calculator to choose anchor times you can maintain.

Night flights and middle‑seat reality: If you cannot sleep on the plane, that is okay. Stick to your arrival light plan and keep naps short. A few nights of steady timing usually matter more than whether you slept in the air.

Common mistakes to avoid

• Shifting too fast and then abandoning the plan entirely — smaller, steady steps are more sustainable.
• Bright screens late at night on eastbound trips — dim devices or use night mode well before bed.
• Heavy evening meals during eastbound adjustment — large meals push sleep later.
• Long, late naps after arrival — keep naps short and early to protect bedtime.
• Skipping morning daylight — a brief walk in sunlight helps more than an extra espresso.

When to consider melatonin

Some travelers use a low dose of melatonin near local bedtime for a few nights, especially after large eastbound shifts. Timing matters more than the perfect dose. Many people start with 0.5–1 mg about 1–2 hours before the target bedtime and adjust based on how they feel. Others prefer not to use it at all. Our calculator includes a brief reminder because timing interacts with light cues.

This is general information, not medical advice. If you have sleep apnea, are pregnant or nursing, or take medications that interact with melatonin, talk to a clinician before using it. Focus first on light and schedule; most of the benefit comes from getting those right.

Helpful tools & links

• Bedtime Calculator — pick a realistic local bedtime you can keep.
• Sleep Cycle Calculator — align sleep timing with 90‑minute cycles.
• Nap Calculator — schedule short, early naps on arrival days.
• Caffeine Calculator — check how long caffeine stays in your system.
• Hydration Calculator — prevent sluggishness caused by low fluids.
• Meditation Timer — use a 5–10 minute wind‑down before bed.
• Insomnia Calculator — reflect on patterns if sleep stays disrupted.

External references (non‑commercial):

• CDC: Jet lag overview
• NHS: Jet lag advice

We avoid medical claims and focus on practical tools. External links are informational and may change over time.

Frequently Asked Questions