Time Calculator
Basic Time Calculator
Add or subtract two time values. Input fields can be left blank, which will be taken as 0 by default.
Add or Subtract Time from a Date
Add or subtract time (days, hours, minutes, seconds) from a starting time and date.
Time Calculator in Expression
Add or subtract time values in the form of an expression. Use d for days, h for hours, m for minutes, and s for seconds.
About Time Measurement
History of Timekeeping
The concept of time has evolved throughout human history. Ancient civilizations used sundials, water clocks, and other devices to measure time.
The modern second is defined based on the radiation frequency of cesium atoms, making atomic clocks the most accurate timekeeping devices.
Time Units
Time is measured in various units: milliseconds, seconds, minutes, hours, days, weeks, months, years, decades, centuries, and millennia.
The Gregorian calendar is the most widely used civil calendar, with 365 days in a common year and 366 days in a leap year.