Jet Lag: How Time Differences Affect You and How to Adjust

Crossing several time zones puts your internal clock out of step with the local one. Knowing the time difference in advance lets you plan the adjustment.

By the VClock team at Digimarket Group SIA · Updated 4 November 2026

Note: General information, not medical advice. Ask a doctor or pharmacist before using sleep medication or melatonin, especially with other medicines or health conditions.

Why jet lag happens

Your body runs on a circadian rhythm of roughly 24 hours, tuned mainly by light. When you fly across time zones, local daylight and meal times no longer match your internal clock. Symptoms include poor sleep, daytime tiredness, difficulty concentrating and digestive upset. Crossing three or more time zones usually produces noticeable effects.

East is harder than west

Most people's internal clock runs slightly longer than 24 hours, so it is easier to delay sleep (westward travel) than to advance it (eastward travel). A rough rule of thumb is that adjustment takes about a day per time zone crossed, often a bit longer going east.

Before you travel

Check the exact time difference for your travel dates — daylight-saving changes can shift it by an hour.
For eastward trips, go to bed and wake up 30–60 minutes earlier for a few days beforehand; for westward trips, shift later.
Set a second clock (or a VClock tab) to destination time so you start thinking in it.

On arrival

Light: after eastward travel, get morning daylight; after westward travel, get late-afternoon light. Light is the strongest signal to your clock.
Meals: eat at local meal times.
Naps: if needed, keep them short (20–30 minutes) and before mid-afternoon.
Caffeine and alcohol: caffeine in the morning can help alertness; avoid both close to local bedtime.

Short trips

For a trip of only one or two days, many travellers keep their home schedule as much as possible rather than adjusting and readjusting.

Working across time zones remotely

Remote workers face a “social jet lag” version: very early or late calls. Rotate inconvenient meeting times fairly across regions and protect sleep windows.