Use the search box above to pin cities for comparison.
Before the 19th century, every town kept its own local solar time — noon was when the sun was directly overhead. This worked fine until railways arrived. In the 1840s, Britain's Great Western Railway became the first to adopt a standardized "Railway Time" (GMT), and by 1880, GMT became the UK's legal time standard.
In 1884, the International Meridian Conference in Washington D.C. established Greenwich as the prime meridian and divided the world into 24 time zones. The modern Coordinated Universal Time (UTC) was adopted in 1972, using atomic clocks for unprecedented precision. Today, all civil time worldwide traces back to UTC maintained by the International Bureau of Weights and Measures (BIPM).
Approximately 70 countries observe Daylight Saving Time, though start and end dates vary significantly. The US switches on the second Sunday of March and first Sunday of November. Europe switches on the last Sunday of March and last Sunday of October. Countries near the equator — including most of Southeast Asia, India, and parts of South America — do not observe DST, as daylight hours remain relatively constant year-round. Notable non-observers: China, Japan, India, and Russia (abolished DST in 2014).
A world clock displays the current local time for multiple cities simultaneously, along with each city's UTC offset. When the offset is UTC+9, the city is 9 hours ahead of UTC. When it's UTC-5, it's 5 hours behind. The DST indicator shows whether summer time is currently active. Use the Time Zone Converter to plan meetings across these time zones.
Type the city name in the search box to select from 50+ major cities worldwide. The clock updates in real-time showing the correct local time for that city, including its UTC offset and DST status.
UTC (Coordinated Universal Time) is the modern atomic time standard used globally. GMT (Greenwich Mean Time) is a time zone based on solar time at the Royal Observatory in Greenwich. In practice, both show UTC+0, but UTC is the technically correct standard — all time zones are defined as UTC±offsets.
There are 38 recognized time zones ranging from UTC−12:00 (Baker Island) to UTC+14:00 (Line Islands, Kiribati). Some regions use non-standard offsets: India uses UTC+5:30, Nepal uses UTC+5:45, and the Chatham Islands use UTC+12:45.
Daylight Saving Time (DST) — also called "summer time" — is the practice of advancing clocks by one hour during warmer months. About 70 countries observe DST. Major exceptions include China, Japan, India, Russia, and most equatorial nations.
This clock uses your device's system clock via JavaScript, which is synchronized with network time servers (NTP) at the operating system level. For everyday use — checking another city's time, planning calls — it is accurate within milliseconds.
The 12-hour clock (with AM/PM) is common in English-speaking countries and parts of Asia and Latin America. The 24-hour clock is standard in most of Europe, in military contexts globally, and in aviation. This tool offers both formats via the toggle.