Jet lag calculator
Choose your departure and destination cities and your travel date. The calculator shows the time shift and direction, roughly how many days your body clock needs to catch up, and a simple light and sleep plan. As a rule, the body adjusts by about one hour a day flying east and a bit faster flying west.
Why jet lag happens
Your body runs on an internal clock of about 24 hours, set mainly by light hitting your eyes. Fly across several time zones and the local clock jumps, but your body clock does not: it keeps telling you to sleep at home's bedtime. Until it catches up you may feel tired by day, wide awake at night, hungry at odd hours and foggy.
Flying east is usually harder, because you have to go to sleep earlier than your body wants, and the natural tendency of most body clocks is to run slightly long, which makes delaying easier than advancing. Research on travellers suggests the body clock shifts by about an hour a day going east and an hour and a half going west, though people vary.
What actually helps
Light at the right time is the strongest signal for resetting the body clock, followed by regular meal and sleep times in the new zone. The plan above follows that rule. If you have a health condition, are pregnant or are thinking about sleep medicine or melatonin, ask a doctor or pharmacist first. Plan calls home with the time zone converter and the meeting planner, and set an alarm for local wake-up time.
Questions people ask
How long does jet lag last?
Roughly a day for each time zone crossed when flying east, and a bit less when flying west. A 6-hour shift east can take about 6 days to fully settle.
Is jet lag worse flying east or west?
East, for most people. You need to fall asleep earlier than your body wants, and body clocks find it easier to delay than to advance.
How can I get over jet lag faster?
Switch to local time at once, get daylight at the right times (see the plan), eat at local mealtimes, keep naps short and go easy on alcohol and late caffeine.
Do you get jet lag flying north or south?
No. Jet lag comes from crossing time zones, so a long flight that stays in one time zone causes tiredness but not jet lag.