Learn how to tell the time in English. We use the time to sequence events, to compare
their duration and the intervals between them, and to quantify the speed at which objects move and things change.
To measure time, we can use anything that repeats itself regularly. One example is the dawn of a new day. Two more are the phases of the moon, and the seasons of the year. Even in ancient times, people developed calendars to keep track of the number of days in a year.
Telling the time in English is more complicated than just reading some numbers from the clock…
Units of Time
- 1 aeon = ~1 billion years (in astronomy)
- 1 millennium = 1000 years
- 1 century = 100 years
- 1 decade = 10 years
- 1 lustrum = 5 years
- 1 year = 12 months ≈ 365 days (366 days in leap years)
- 1 month ≈ 28 to 31 days ≈ 4 weeks
- 1 fortnight = 14 days = 2 weeks
- 1 week = 7 days
- 1 day = 24 hours
- 1 hour = 60 minutes
- 1 minute = 60 seconds
- 1 second = SI base unit of time
- 1 millisecond = 1/1,000 second
- 1 microsecond = 1/1,000,000 second
- 1 nanosecond = 1/1,000,000,000 second
- 1 picosecond = 1/1,000,000,000,000 of a second
- 1 femtosecond = 1/1,000,000,000,000,000 of a second
- 1 attosecond = 1/1,000,000,000,000,000,000 of a second
- 1 Planck time = smallest measurable unit of time
