Jet Lag Adjustment Simulator
This Jet Lag Adjustment Simulator is based on concepts from sleep medicine and chronobiology. It estimates when to seek bright light and when to avoid bright light, based on your time zone difference and travel schedule.
You can check a personalized light-adjustment pattern from pre-trip preparation to post-arrival adaptation, helping you plan how to support your body clock before, during, and after travel.
Simulation result
---
Action timeline
| Date | Phase | Get light | Avoid light |
|---|
Important Notice
The results provided by this tool are not intended for medical diagnosis or treatment. The displayed times and estimated number of days are general behavioral guidelines based on how light exposure affects the body clock.
How you experience jet lag and how quickly you adjust may vary depending on individual factors such as your physical condition, lack of sleep, sleep during travel, local schedule, and light intensity.
Basic Rules
- ・If specific times are shown in the results, prioritize the actions recommended during those time windows.
- ・During the times shown under “Seek Light,” try to stay in a bright environment, such as outdoors in natural light, near a window, or in a well-lit room.
- ・During the times shown under “Avoid Light,” reduce exposure to strong light by using sunglasses, staying in the shade, choosing dimmer indoor lighting, or lowering screen brightness.
- ・While sleeping, use an eye mask, blackout curtains, or other methods to block outside light as much as possible.
- ・If “—” is shown, there is no specific time window assigned. In that case, follow the local schedule: keep your environment bright while awake, and keep it dim before bedtime and during sleep.
How to Use
- Departure location: Select the country and city you are departing from.
- Destination: Select the country and city you are traveling to.
- Departure date and time: Enter the departure time in the local time of your departure location.
- Arrival date and time: Enter the arrival time in the local time of your destination.
- Usual sleep rhythm: Select your typical bedtime and wake-up time.
- Preparation days before departure: Select how many days you can adjust your daily rhythm before departure.
When to Use This Tool
Before International Travel
Use this tool before international travel to check when to seek light and when to avoid light. This can serve as a practical guide for reducing sleepiness, fatigue, and rhythm disruption after arrival.
After Arriving at Your Destination
After arrival, use the timeline to see when you should spend time in a bright environment and when you should avoid strong light. This can help support adaptation to the local time zone.
Before an Overseas Business Trip
If you have meetings, negotiations, or work soon after arrival, this tool can help you prepare your body clock in advance so that you can better align with the destination’s local schedule.
After Returning Home
After returning from overseas travel, you can use this tool as a guide to help shift your daily rhythm back toward your usual schedule.
Overview
This tool is a simulation tool focused on light-based jet lag adjustment. It is based on the relationship between the body clock and light, a key concept in sleep medicine and chronobiology.
Using the concept of the phase response curve, the tool estimates when to seek light and when to avoid light. Unlike a basic time zone calculator that only shows the time difference between departure and destination, this simulator creates a timeline-based adjustment plan that takes into account your preparation days before departure and your travel schedule.
Phase Response Curve (PRC): A response curve showing how light exposure at different times can shift the body clock earlier or later.
Basic Knowledge
▶︎Jet Lag
Jet lag is a temporary disruption that occurs when your internal body clock is out of sync with the local schedule at your destination.
Common symptoms may include daytime sleepiness, difficulty sleeping at night, trouble waking up, reduced concentration, fatigue, and changes in appetite or digestive rhythm.
Because the body does not instantly switch to the destination’s local time, sleep and physical condition can remain unstable for several days after arrival.
▶︎Body Clock
The body clock is the internal timing system that helps regulate sleep, wakefulness, body temperature, hormone secretion, appetite, and other daily rhythms.
Human biological rhythms follow a cycle of roughly 24 hours. When this rhythm no longer matches the day-night cycle at your destination, sleep and physical condition can become disrupted.
For jet lag adjustment, the goal is to gradually shift the body clock closer to the local time at your destination.
▶︎Light and the Body Clock
Light is one of the most important signals for adjusting the body clock. Light entering the eyes is transmitted to the suprachiasmatic nucleus, a central clock region in the brain that helps regulate the sleep-wake rhythm.
For jet lag adjustment, it is important not only to know when to seek light, but also when to avoid light.
Strong sunlight and bright indoor lighting can affect the body clock. Even when the eyes are closed, some light can pass through the eyelids, so light exposure during sleep or naps may still influence circadian timing.
For this reason, jet lag adjustment is not simply about “getting morning light.” The timing of light exposure and light avoidance should be considered based on the direction of travel and the time zone difference.
▶︎Why Pre-Trip Preparation Matters
If you have several days before departure, gradually adjusting when you seek light and avoid light can help reduce the remaining time shift at arrival.
However, pre-trip preparation cannot completely eliminate jet lag. It should be understood as a practical way to support adaptation after arrival.
Specifications
Departure Location and Destination
The departure location and destination are used to identify each time zone and calculate the time difference before and after travel.
This tool uses the destination time as a reference to estimate the gap between the local schedule and your current body clock, then determines the likely direction of light-based adjustment.
Departure and Arrival Date/Time
Departure and arrival times are used to separate the timeline into pre-trip, in-transit, and post-arrival phases.
Before departure, the tool uses the local time at the departure location. After arrival, it uses the local time at the destination. For each day, it displays suggested windows for seeking light and avoiding light.
Usual Sleep Rhythm
Your usual bedtime and wake-up time are used to estimate your baseline sleep-wake rhythm.
The wake-up time is especially important because it is used as a reference point to estimate the timing of the core body temperature minimum, a key marker of circadian timing.
Preparation Days Before Departure
The number of preparation days is used to estimate how much your body clock may be shifted toward the destination time before travel.
After accounting for the amount that can be adjusted before departure, the tool estimates the remaining time gap at arrival and the number of days needed to adapt to the local time.
This tool estimates when to seek light and when to avoid light based on the concept of the Phase Response Curve (PRC), which describes how the timing of light exposure can shift the body clock earlier or later.
In general, bright light before the core body temperature minimum tends to delay the body clock, while bright light after the core body temperature minimum tends to advance it.
The core body temperature minimum usually occurs a few hours before habitual wake time. Therefore, this tool estimates a circadian reference point from your usual wake-up time and compares it with the destination time to determine when light exposure or light avoidance is likely to be useful.
The body clock does not shift dramatically all at once. As a general estimate, advancing the body clock often progresses by about 1 hour per day, while delaying the body clock may progress by about 1.5 hours per day.
This tool uses those adjustment estimates to calculate how much can be adjusted before departure, how much time difference may remain at arrival, and how many days it may take to adapt to the local time.
FAQ
Q. If I follow this tool, can I completely prevent jet lag?
A. Not necessarily. This tool provides general guidance for jet lag adjustment based on the relationship between the body clock and light. Individual experience and adaptation speed can vary depending on factors such as personal physiology, sleep debt, sleep during travel, and your schedule after arrival.
Q. What exactly should I do during “Seek Light”?
A. Ideally, spend time outdoors in natural light. If that is difficult, staying near a window or spending time in a bright indoor environment can also help. The goal is to send a “daytime activity” signal to your body clock.
Q. Does “Avoid Light” mean I need to stay in complete darkness?
A. No. The goal is to reduce exposure to strong light, not necessarily to stay in total darkness. Practical options include wearing sunglasses, avoiding bright lighting, reducing smartphone or computer screen brightness, and spending time in a dimmer environment.
Q. Can I use this tool if I have 0 preparation days before departure?
A. Yes. Even if you cannot prepare before departure, the tool can still show light-adjustment guidance for the travel period and after arrival. If you are busy until the last minute, you can use it as an action plan after reaching your destination.
Q. Why do eastward and westward travel produce different results?
A. The body clock often adjusts more easily when it is delayed than when it is advanced. For this reason, eastward travel can take longer to adapt to, while westward travel may be easier for many people. This tool uses that difference to estimate the adjustment direction and adaptation period.
Q. Does this tool include sleep duration, caffeine, or melatonin in the calculation?
A. No. This tool focuses on when to seek light and when to avoid light as part of jet lag adjustment. Sleep duration, caffeine, and melatonin can also affect jet lag, but the appropriate approach can vary depending on health status, medication use, and individual circumstances, so they are not included in the calculation.
Q. Can children or older adults use this tool?
A. It can be used as general guidance. However, children and older adults may be more sensitive to changes in sleep rhythm and physical condition, so the results should be used within a comfortable and realistic range.
Q. Can I use this tool if I have insomnia or a sleep disorder?
A. If you have insomnia, a sleep disorder, or significant health concerns, jet lag adjustment may require additional care. Consider consulting a healthcare professional when needed.
Ver 1.0.0
Feedback
Please share your feedback to help us improve our tools.