# TIME UNIT CONVERSION CALCULATOR

 second s minute min hour h day d week wk month (1/12 avg cal year) mo calendar year (365 day) a calendar leap year (366 day) a calendar year (average) a tropical year (astronomy) a

### Time

Definition:
Time is a fundamental quantity which cannot be defined in terms of classical or newtonian quantities. The SI base unit of time is the second and is defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. This gives the unit second a stable unchanging reference value unlike references from the motion of the sun and planets.

Time can be measured either in "days of fixed length": SI days of 86400 SI seconds, defined by the atomic clocks, or dynamical days defined by the motion of the Moon and planets); or in "natural" days, defined by the rotation of the Earth with respect to the Sun. The duration of the natural day is steadily getting longer as measured by the SI second.

At the epoch J2000 (1 January 2000, 12h TT), the mean tropical year was: 365.242189670 SI days. Due to changes in the precession rate and in the orbit of the Earth, there exists a steady change in the length of the tropical year (about 5 ms/year). This means that in 2000 years time the tropical year will be about 10 seconds shorter.

The calculator uses the SI second, minute and hour. The week is based on a seven SI days. The month is based on 1/12 average calendar year.

## Convert between Different Units of Measurement

 Index of Unit Converters

To use the measurement conversion calculators simply enter a number value into the desired field and click calculate. All results shown will be equivalent values. Values are given to seven significant figures ( the odd result may show 9's or 0's over running). Values of 10 000 or greater will be displayed in the e-format e.g. 2.3456e7 which equals 2.3456 x 107 or 23 456 000. Values lower than 0.001 will be displayed in the e-format e.g. 2.3456e-5 which equals 2.3456 x 10-5 or 0.000 023456. The calculators require that your browser has java script enabled. View all measurement unit conversion calculators on the same page (may not work with all browsers; requires Iframe).

Si Units:

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