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Calculate circadian rhythm phase shift schedules, optimal melatonin timing, photic light exposure and darkness windows, and sleep adjustment strategies based on time zones crossed and travel direction.
sim 1.5 ext{ hours/day}; Eastward phase advance adapts more slowly at sim 1.0 ext{ hour/day}. ext{CBTmin} approx 5:00 ext{ AM} (2 hours prior to habitual wake time). Light exposure after CBTmin advances the clock; light before CBTmin delays it.The natural human circadian pacemaker (in the suprachiasmatic nucleus) operates on an endogenous cycle slightly longer than 24 hours (~24.2 hours). Traveling westward requires phase delay (lengthening the day and staying up later), which works with your biology. Traveling eastward requires phase advancement (shortening the day and falling asleep earlier), which works against your natural rhythm.
CBTmin is the point in your 24-hour cycle when your internal temperature drops to its lowest level, usually occurring about 2 hours before your habitual wake-up time (e.g. 5:00 AM for a 7:00 AM riser). Exposing your eyes to bright light in the hours immediately AFTER CBTmin forcefully advances your clock, while light BEFORE CBTmin pushes your clock backward.
Clinical chronobiology studies recommend low-dose melatonin (0.5mg to 3mg) taken 30 to 60 minutes before your target destination bedtime on the night of arrival and for the subsequent 3–4 nights. For eastward travel, taking a microdose in the late afternoon of home time before travel can jumpstart circadian phase advance.
Peripheral metabolic clocks in your liver, gut, and pancreas synchronize to meal timing rather than light. Fasting during your flight and eating a protein-rich breakfast at destination morning time acts as a powerful secondary zeitgeber ('time-giver'), locking your digestive and energy systems to the new timezone.