How does light exposure reset the circadian rhythm?

Intrinsically photosensitive retinal ganglion cells (ipRGCs) in your eyes detect blue wavelengths (460–480 nm) in daylight and transmit signals directly to the suprachiasmatic nucleus (SCN) in the hypothalamus, instantly halting melatonin production and setting your biological clock to daytime.

When should I take melatonin for jet lag?

For eastward travel across multiple time zones, take a low dose (0.5 mg to 3 mg) of melatonin approximately 30 minutes before your planned bedtime in your new destination. Avoid taking melatonin upon waking or during the local destination daytime.

How does flight distance and speed factor into flight time calculation?

TimeNumbers calculates flight duration using great-circle orthodromic distance (the shortest route over the curved Earth surface), calibrated for modern commercial passenger aircraft cruising speeds (820–850 km/h) plus standard runway taxi and approach buffers.

Aviation Chronobiology & Travel Optimization

Flight Time & Jet Lag Calculator

Calculate accurate international flight travel times, local arrival hours, and get a chronobiology-backed circadian light and sleep prescription to eliminate jet lag.

Great Circle Orthodromic Routes

Hour-by-Hour Light Prescription

East/West Phase Adaptation

Flight Route & Travel Details

Departure City

Destination City

Departure Date

Departure Time (Local)

Flight Dynamics

7h 47m

Great Circle Distance: 5,837 km (~3,627 miles)

Arrival: Sat, Sep 19, 8:17 AM

Time Shift & Direction

+6h Ahead

Direction: Eastward (Phase Advance)

Challenging adaptation (day is cut short)

Circadian Severity

Severe Circadian Shift

Estimated Biological Adaptation: ~8 days without circadian protocol

Can reduce to ~3 days following the protocol below.

Chronobiology Prescription

Personalized Circadian Protocol in Paris

Timed light exposure and darkness cues directly regulate the suprachiasmatic nucleus (SCN) master clock.

Morning (08:00 – 11:00)

Seek Bright Outdoor Sunlight

Expose eyes to natural sunlight or 10,000-lux lamp for 30–45 mins. This suppresses morning melatonin and advances your circadian rhythm forward.

Afternoon (14:00)

Strict Caffeine Cutoff

Cease coffee, tea, and energy drinks. Adenosine receptors must clear so sleep pressure can build for the earlier bedtime.

Evening (19:00 – 21:00)

Avoid Blue Light & Wear Sunglasses

Dim indoor lighting, activate night shift filters on devices, or wear amber blue-blocking glasses to stimulate pineal melatonin synthesis.

Bedtime (22:00 – 23:00)

Target Sleep Window & Melatonin

Take 0.5mg – 3mg melatonin 30 minutes before destination bedtime. Keep the bedroom completely dark and cool (18°C / 65°F).

Frequently Asked Questions About Jet Lag & Circadian Adaptation

Learn the scientific principles behind circadian phase shifts and recovery protocols.

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The human circadian master clock naturally runs slightly longer than 24 hours (around 24.2 hours). Flying West requires extending your day ('phase delay'), which is biologically natural. Flying East requires compressing your day ('phase advance'), forcing your brain to fall asleep hours earlier than your internal biological clock expects.

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