Time Zone Converter

The UK uses Greenwich Mean Time (GMT, UTC+0) in winter and British Summer Time (BST, UTC+1) from the last Sunday in March to the last Sunday in October. This calculator accounts for the current daylight saving status automatically when converting between UK time and other zones. Many countries change their clocks on different dates, or never change them at all, so the tool works from the IANA time zone database to keep those differences straight, shows the current time in both locations, and flags any crossing of the date line. For business use it also displays the overlapping working hours between two zones, which is how you arrange a call without asking anyone to join at midnight.

The British clock change is set by a rule rather than by a fixed date. Clocks go forward one hour at 1am on the last Sunday in March and back at 2am on the last Sunday in October, so in 2026 BST starts on 29 March 2026 and ends on 25 October 2026. In British usage the daylight saving period is simply called BST, never Eastern or Pacific time, which are American terms. Northern Ireland follows the rest of the UK, and the Republic of Ireland keeps step under the name Irish Summer Time.

Measured from a UK winter, New York sits at UTC−5, Los Angeles at UTC−8, Dubai at UTC+4, Mumbai at UTC+5:30, Singapore and Hong Kong at UTC+8, Tokyo at UTC+9, and Sydney at UTC+10, or UTC+11 in the Australian summer. Once the UK moves to BST the whole picture shifts by an hour, except where the other zone is also changing its own clocks at a different point in the year. Financial desks live by the overlaps, with London and New York sharing 13:00-16:30 UK time, the most liquid stretch of the forex day, and London meeting Asia at around 08:00-09:00 UK time.

A concrete case makes the arithmetic clearer. At 14:00 BST in the UK, New York is on EDT at UTC−4 and reads 09:00, five hours behind. If both offices keep to a nine to five day, the shared window runs 14:00–17:00 UK time, which is 09:00–12:00 in New York. Three usable hours is not much, and it explains why so much transatlantic work lands in the British afternoon rather than the morning.

Australia stretches the working day past breaking point. Sydney runs 9-11 hours ahead of the UK depending on where both countries sit in their own daylight saving cycles, with the widest gap from November to April, when the UK is on GMT and Australia on AEDT. The only real overlap is UK 6-9am against Sydney 5-8pm, which is why most UK and Australian teams work asynchronously through email and Slack instead of trying to meet live. The abbreviations repay learning, since AEST is UTC+10, AEDT UTC+11, JST UTC+9, IST UTC+5:30 and EST UTC−5.

Whether the clocks will keep changing at all is still an open question. The EU voted in 2019 to abolish the twice-yearly change from 2021, but member states could not agree which time to keep and the plan has been shelved indefinitely. The UK left the EU in 2020 and now decides for itself. A UK government consultation in 2023 found 64% in favour of keeping the changes, and Northern Ireland adds a further complication, because abolishing daylight saving on one side of the Irish border and not the other would open a time gap on the island. No bill is before Parliament, so UK clocks will change in 2026 as usual.

The framework all of this rests on was settled at the Royal Observatory Greenwich, where the meridian at 0° longitude was fixed in 1884. Practice since then has been anything but tidy. Russia spans 11 time zones, while China runs a single official zone from Beijing across 5,000km. India sits at UTC+5:30 and Nepal at UTC+5:45, both offset by part of an hour. Antarctic bases generally adopt New Zealand or Chilean time. Either side of the date line, UTC+12 and UTC−12 are a full day apart, so neighbouring Pacific islands can be on different dates at the same moment.