London is UTC+0 (GMT) / UTC+1 (GMT+1). New York is UTC−4 (EDT) / UTC−5 (EST). New York is currently 5 hours behind London.
Best times to meet (London local time): 2:00 PM — 9:00 AM in New York; 3:00 PM — 10:00 AM in New York; 4:00 PM — 11:00 AM in New York.
Times shown in London local time → New York local time. Based on business hours 09:00–17:00.
London operates on Greenwich Mean Time (GMT, UTC+0) in winter and British Summer Time (BST, UTC+1) from late March to late October. The city sits at the Prime Meridian — longitude 0° — established at the Royal Observatory in Greenwich in 1884 when the International Meridian Conference adopted Greenwich as the world's reference point for time and longitude. The GMT standard was already in widespread use because of Britain's dominance in maritime navigation and the railway network, which demanded a single national time to replace the patchwork of local times that differed by minutes from town to town.
The UK introduced Daylight Saving Time during World War I in 1916, following Germany's lead, to reduce coal consumption by extending evening daylight. Today DST is governed by EU rules (retained in UK law post-Brexit), meaning the clocks change on the last Sunday of March and October. London is one of the world's most important financial centres: the London Stock Exchange opens at 08:00 GMT and closes at 16:30, overlapping with Asian market closes in the morning and US market opens in the afternoon — a position that helps make London the largest foreign-exchange trading centre on earth.
Because London is UTC+0 in winter, it serves as a natural reference point for international scheduling. A meeting at "noon UTC" is noon in London from November to March. The city is 5 hours ahead of New York (EST) in winter and 8 hours behind Tokyo (JST), making it the pivot of East–West business communication.
New York City observes Eastern Time: UTC−5 (EST, Eastern Standard Time) from the first Sunday in November to the second Sunday in March, and UTC−4 (EDT, Eastern Daylight Time) during the remainder of the year. The Eastern Time Zone covers roughly a third of the US population and all of Canada's most populous provinces, making EST/EDT the de-facto "American" timezone in global business. The US adopted standard time nationally after the Standard Time Act of 1918, and year-round Daylight Saving Time rules were made permanent by the Energy Policy Act of 2005.
New York's financial markets — the New York Stock Exchange and NASDAQ — open at 09:30 and close at 16:00 EST/EDT, setting the rhythm for global equity trading. The city is 5 hours behind London (in winter), 14 hours behind Tokyo, and 9.5 hours behind Mumbai, which means scheduling live meetings between New York and Asia almost always requires someone to work outside normal hours. New York is 3 hours ahead of Los Angeles, so the US business day effectively runs from 06:00 Pacific to 17:00 Eastern — an 11-hour window.
The Uniform Time Act of 1966 standardised DST observance across US states, though states can opt out (Arizona does not observe DST, and Hawaii has never observed it). There are periodic debates in the US Congress about eliminating the clock change entirely, similar to EU proposals. Until such a change occurs, New York switches twice per year, occasionally causing brief periods where the offset to London or other regions differs from the norm by one hour during the transition weeks when the two regions change on different dates.
New York is currently 5 hours behind London.
When it is 12:00 noon in London, it is 07:00 in New York (based on current offsets — verify during DST transitions).
London observes DST, changing from GMT to GMT+1. New York observes DST, changing from EDT to EST.