London operates on Greenwich Mean Time (GMT) during winter months, which is Coordinated Universal Time (UTC+0). During daylight saving time, observed from the last Sunday in March to the last Sunday in October, London switches to British Summer Time (BST), which is UTC+1.
London is the capital of the United Kingdom and one of the world's most important financial centers. The Greenwich meridian (0° longitude) passes through London, making it the historical reference point for world time zones. When scheduling calls with New York, London is 5 hours ahead (4 hours during BST).
The Royal Observatory in Greenwich, London, is where Greenwich Mean Time originated in 1884. Big Ben, the famous clock tower at the Houses of Parliament, has been keeping London time since 1859 and is accurate to within one second. London's position at UTC+0 makes it a natural hub for global business coordination.