About this tool
This converter turns a time in New York into the matching time in London, or the other way round, for any date you choose. It shows both cities' current clocks live, the hour difference in force on the chosen date, whether each city is on daylight saving time, a 24-hour conversion table for that day with the 9-to-5 overlap marked, and the exact dates of this year's clock changes in both cities. London is usually five hours ahead of New York, but for a few weeks each spring and autumn the gap shrinks to four because the United States and the United Kingdom change their clocks on different Sundays; the year table shows exactly when. It is built for people scheduling transatlantic calls, watching UK or US broadcasts, or booking travel between the two cities.
How it works
Both cities are IANA time zones (America/New_York and Europe/London) and every offset comes from the browser's time zone database through Intl.DateTimeFormat, never from a hard-coded table, so the daylight-saving rules in force on the chosen date are applied automatically. To convert, the wall-clock time you enter is first treated as UTC, the source zone's offset at that guess is subtracted, and the check is repeated once so times on a clock-change day land on the correct side of the change. The resulting instant is then formatted in the other zone to give the local date and time; the day marker is the difference between the two calendar dates. The hour difference shown is the target offset minus the source offset at that instant, and the year table is built by sampling the two offsets at noon UTC on every day of the year and grouping the runs where the difference stays the same.
Frequently asked questions
Is London 5 or 4 hours ahead of New York?
Five for most of the year, four for a few weeks. The United States moves to daylight saving time on the second Sunday in March while the United Kingdom waits until the last Sunday in March, and the UK ends British Summer Time on the last Sunday in October while the US keeps daylight time until the first Sunday in November. In 2026 the gap is 4 hours from March 8 to March 28 and from October 25 to October 31.
When do the clocks change in New York and London?
New York: second Sunday in March at 2:00 am (forward to EDT) and first Sunday in November at 2:00 am (back to EST). London: last Sunday in March at 1:00 am GMT (forward to BST) and last Sunday in October at 2:00 am BST (back to GMT). The clock-changes table on this page lists the exact dates for whatever year you pick.
Is it ever the next day in London?
Yes, whenever it is 7:00 pm or later in New York (8:00 pm during the 4-hour weeks). A 9:00 pm call in New York is 2:00 am the following morning in London, which is why late US evening events carry a next-day date in the UK. Conversely, before 5:00 am in London it is still the previous evening in New York.
What are the best hours for a New York to London call?
9:00 am to noon in New York, which is 2:00 pm to 5:00 pm in London, is the only stretch that falls inside both standard 9-to-5 working days, three hours in total. 8:00 am New York (1:00 pm London) is a common compromise that leaves the New York afternoon free, and 1:00 pm New York catches London at 6:00 pm for people who work slightly later.