How far ahead is London?
For most of the year London is 5 hours ahead of New York: when it’s noon in New York, it’s 5:00 PM (17:00) in London. Both cities use daylight saving time, but they change their clocks on different dates. The US switches on the second Sunday in March and the first Sunday in November; the UK switches on the last Sunday in March and the last Sunday in October.
That leaves a few weeks each year when the gap is only 4 hours. In 2026 that happens from March 8 to March 28 and from October 25 to October 31. The calculator above uses your browser’s time-zone data, so it picks up these changes for whatever date you enter.
Why flying east to London is often harder
Flying from New York to London asks your body clock to move 5 hours earlier. You land in the morning, London time, when your body still thinks it’s the middle of the night, and at bedtime in London it can feel like early evening.
Most people find it harder to shift their body clock earlier than later, which is why eastward trips tend to cause more jet lag than westward ones. Adjusting usually takes several days. How long it takes you depends on your own sleep, how well you slept on the flight and what you do after you land.
Shifting your schedule before you fly
The example plan moves your wake-up time and bedtime 30 minutes earlier on each of the three days before you leave. By departure day, you’re 90 minutes closer to London time, so there’s less of a gap to close after you land.
Small steps are easier to stick to than one big change. If an earlier bedtime clashes with work or family, don’t force it: even one or two days helps a little, and a good night’s sleep before you fly matters more than following the plan exactly.
On arrival in London
- Switch to London time as soon as you board: set your watch and phone, and plan meals around London times.
- Spend time outdoors in daylight during your first days. Daylight is one of the strongest signals for your body clock.
- If you’re exhausted, a short nap of under 30 minutes is fine, but avoid long afternoon sleeps that make bedtime harder.
- Keep caffeine to the morning and go easy on alcohol, which can make sleep lighter. The caffeine cutoff for a 10 PM bedtime shows one way to plan it.
Some people consider melatonin or sleep medicine for jet lag. Whether either is right for you depends on your health and other medicines, so ask a doctor or pharmacist first.
Coming back to New York
The return trip is westward, so your body clock needs to move later instead. Most people find this easier. Staying up until a normal New York bedtime and getting daylight during the day usually does most of the work.
More answers
- Bedtime for a 4 AM wake-upRelated answer
- Bedtime for a 4:15 AM wake-upRelated answer
- Bedtime for a 4:30 AM wake-upRelated answer
- Bedtime for a 4:45 AM wake-upRelated answer
Frequently asked questions
How many hours ahead is London from New York?
Usually 5 hours. For a few weeks in March, and from late October to early November, the two countries’ clock changes don’t line up and the difference is 4 hours. Enter your travel date above to check.
Is jet lag worse flying from New York to London?
For many people, yes. Flying east means your body clock has to move earlier, which tends to be harder than moving later. The return flight to New York is often easier to adjust to.
Should I sleep on the flight to London?
On an overnight flight, sleeping as much as you can usually helps. An eye mask, earplugs and skipping alcohol can make it easier. Then try to stay awake until a normal London bedtime.
Related calculators
Bedtime calculator
Enter any wake-up time to see bedtimes that let you wake between sleep cycles.
Wake-up time calculator
Going to bed now or at a set time? Find wake-up times that land at the end of a cycle.
Nap calculator
Plan a 10-, 20- or 90-minute nap and see when to set your alarm.
Sleep debt calculator
Add up the last seven nights and see how far you are from your sleep target.
Sources
- Centers for Disease Control and Prevention. CDC Yellow Book: Jet Lag.
- NHS. Jet lag.
- Sack RL. Jet lag. New England Journal of Medicine, 2010;362(5):440–447. doi:10.1056/NEJMcp0909838.
- Internet Assigned Numbers Authority. Time Zone Database.
When to seek help
Talk to a doctor before you travel, or when you’re back, if you:
- have a sleep disorder, heart condition, diabetes or another long-term condition, or are pregnant;
- are thinking about melatonin, sleeping tablets or any other medicine for jet lag;
- still have poor sleep, low mood or daytime sleepiness a couple of weeks after your trip;
- travel across time zones often and find it’s affecting your health or work.