GMT (Greenwich Mean Time)
gmt
The mean solar time at the Royal Observatory in Greenwich, London, historically used as the international time reference.
UTC (Coordinated Universal Time)
utc
Overview
UTC (Coordinated Universal Time) is the primary time standard used worldwide to regulate clocks and time. It is the successor to GMT and is maintained by the International Bureau of Weights and Measures (BIPM) using a network of highly precise atomic clocks distributed across the globe.
How It Works
UTC is based on International Atomic Time (TAI) but incorporates leap seconds to remain within 0.9 seconds of mean solar time at the Prime Meridian. This ensures that UTC stays aligned with the Earth's rotation while maintaining the precision of atomic timekeeping.
Practical Use
All time zones are defined as offsets from UTC, ranging from UTC-12 to UTC+14. Aviation, computing, scientific research, and international communications all rely on UTC as their reference standard to avoid ambiguity across regions.
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