The base unit to measure time is the second.
Quantitatively, the second is defined by a number of oscillations (exactly 9 192 631 770) of a cesium atom. Measuring and counting these oscillations is carried out by electronic clocks. It is a very precise measurement.
The usual symbols used for time measurement are:
- second : s
- minute : min
- hour : h
- 1 millenium is equal to 1000 years
- 1 century is equal to 100 years
- 1 decade is equal to 10 years
- 1 lustrum is equal to 5 years
- 1 year is equal to 12 months or to 52 weeks or to 365 days
- 1 week is equal to 7 days
- 1 day is equal to 24 hours
- 1 hour is equal to 60 minutes
- 1 minute is equal to 60 seconds