Jet Lag Recovery Time Calculator

Jet Lag Recovery Time depends on the number of time zones crossed, the direction of travel, and personal factors like age.

The general rule: Your body adjusts approximately 1-1.5 time zones per day when traveling eastward, and 1.5-2 time zones per day when traveling westward.

Eastward vs. westward travel:

• Eastward travel is harder because you must advance your sleep schedule (go to bed earlier). This fights your natural tendency to stay up later.
• Westward travel is easier because you delay your sleep schedule (stay up later). Most people find it easier to stay up than to fall asleep early.

Recovery formula:

• Eastward: Recovery Days ≈ Time Zones × 1.0 (approximately 1 day per zone)
• Westward: Recovery Days ≈ Time Zones × 0.67 (approximately 2/3 day per zone)

Age adjustments:

Worked examples: New York to London, 5 zones eastward, a traveller in their forties: 5 × 1.0 × 1.00 = 5 days. London to Los Angeles, 8 zones westward, same traveller: 8 × 0.67 × 1.00 = 5.4 days. That same westward trip for someone over 65: 8 × 0.67 × 1.50 = 8 days.

The result is shown as a range, the central figure plus or minus a quarter, because individual variation is genuinely large and a single number would be false precision.

Symptoms, and roughly when to expect them:

Note that the digestive symptoms clear first and the sleep disruption last. Your gut has its own clock and it resets faster than your brain does, which is why you feel normal at meals several days before you can sleep through the night.

Before the flight:

• Shift your sleep 2–3 days before departure: earlier for eastward, later for westward.
• Stay hydrated and skip the alcohol on the plane.
• If you can choose, take a flight that lands in the evening local time. Going straight to bed is far easier than filling a day you did not sleep for.

After arrival:

• Get onto local time immediately and stay up until at least 9 or 10 PM local.
• Morning sunlight if you flew east, afternoon sunlight if you flew west. Light at the wrong end of the day pushes your clock the wrong way and makes things worse, not merely slower.
• Naps of 20 to 30 minutes are fine. Longer ones will cost you the night.
• No caffeine after 2 PM local time.

Factors that make it worse:

• Crossing more than 8 time zones
• Older age, since circadian adaptation genuinely slows
• Arriving already sleep-deprived from the days before travel
• Alcohol and dehydration in the air
• Staying in low light all day after you land

Crossing the date line (12+ hours difference): Your body adjusts by whichever route is shorter, which is not always the direction you flew. At exactly 12 zones the two are equal and it will pick one more or less at random.

Frequent flyers who cross zones repeatedly without a full recovery in between can end up with chronic circadian disruption, which is a different and more stubborn problem than ordinary jet lag.