Why Circadian Rhythm Matters

Your circadian rhythm is your body’s internal clock. Crossing time zones too quickly can leave it out of sync, causing fatigue and grogginess. Researchers generally find that most people can comfortably shift their sleep schedule by about one hour per day. Strategic exposure to light and darkness can accelerate this process slightly, but huge leaps still take several days.

The Adjustment Equation

The planner estimates days needed to adapt based on a simple division. If is the difference in hours between your current zone and your destination, and is how many hours you can shift your schedule each day, the number of days is:

Because the absolute value is used, flying east or west results in the same adjustment time. If you prefer, you can experiment with shifting more aggressively before departure, effectively increasing .

Tips for Smooth Travel

Start adjusting a few days before leaving by going to bed earlier or later depending on your direction of travel. Upon arrival, seek bright light in the morning if you need to advance your schedule, or in the evening if you must delay it. Avoid heavy meals and alcohol late at night, as these can disrupt sleep even further.

Example Schedule Table

The table below shows a hypothetical 6-hour eastward jump with a two-hour shift possible each day. It demonstrates how you might move bedtime earlier until it aligns with your new location.

Day	Target Bedtime
Departure Day	11:00 PM
+1	9:00 PM
+2	7:00 PM
+3	5:00 PM

Although personal rhythms differ, gradually nudging sleep and wake times helps most travelers feel functional sooner.

Looking After Your Health

Lack of sleep can impair thinking, mood, and immune function. If possible, give yourself a buffer day to rest after arriving, especially on very long trips. Staying hydrated and spending time outdoors helps signal your body that it’s time to reset.