timemeasurement

Timemeasurement is the practice of quantifying temporal intervals and moments so that events can be ordered, compared, and coordinated. It involves determining elapsed time between events, assigning timestamps, and measuring the rate of processes.

The SI base unit of time is the second. A second is defined by the cesium-133 atomic transition. Larger and smaller units are derived as minutes, hours, days, milliseconds, microseconds, and nanoseconds. International time scales such as TAI (International Atomic Time) and UTC (Coordinated Universal Time) provide a uniform reference; UT1 reflects Earth's rotation. Leap seconds are occasionally inserted into UTC to keep it aligned with UT1.

Time is measured with devices called clocks or chronometers, which rely on periodic phenomena. Quartz crystal oscillators provide stable frequencies in many devices; mechanical clocks use gears and pendulums; atomic clocks use atomic transitions for extreme accuracy. Historically, sundials, water clocks, and hourglasses measured solar or flow-based time before mechanical clocks appeared.

Relativistic effects can affect precise time measurement, especially in satellites and high-speed systems. Gravitational time dilation and relative motion require corrections when synchronizing distant clocks. Time can be transferred via radio signals, satellite navigation systems, fiber networks, or internet protocols like NTP.

Timemeasurement supports science, navigation, telecommunications, computing, finance, and many daily activities. Its history spans ancient sundials to modern atomic clocks, and its standards enable global coordination of travel, communication, research, and commerce.