The following table shows the most common time units and their durations.
| Unit | Definition |
|---|---|
| millennium | 1,000 years |
| century | 100 years |
| decade | 10 years |
| year (average) | 365.242 days or 12 months |
| common year | 365 days or 12 months |
| leap year | 366 days or 12 months |
| quarter | 3 months |
| month | 28-31 days January, March, May, July, August. October, December - 31 days April, June, September, November - 30 days. February - 29 days for leap year and 28 days for common year |
| week | 7 days |
| day | 24 hours or 1,440 minutes or 86,400 seconds |
| hour | 60 minutes or 3,600 seconds |
| minute | 60 seconds |
| second | base unit |
| millisecond | 10-3 second |
| microsecond | 10-6 second |
| nanosecond | 10-9 second |
| picosecond | 10-12 second |
The SI unit of time is Second. Also, we can call it a base unit of time. We can easily observe seconds and count them. There are some more units of time such as milliseconds, microseconds, and nanoseconds. Those are smaller than the second. In addition, there are also some bigger time units like minutes, hours, days, weeks, months, and years.
