basic time periods
Year | Time taken by the Earth to revolve around the Sun, or 365.24 days |
Leap Year | Calendar year of 366 days, 29 February being the additional day. It offsets the difference between the calendar year (365 days) and the solar year |
Month | Approximate time taken by the Moon to revolve around the Earth. The 12 months of the year in fact vary from 28 days (29 in a Leap Year) to 31 days |
Week | Artificial period of 7 days, not based on astronomical time |
Day | Time taken by the Earth to complete one rotation on its axis; 1 day = 24 hours = 1440 minutes = 86,400 seconds |
Hour | 24 hours make one day. Usually the day divides into hours AM (ante meridiem, or efore noon) and PM (post meridiem, or after noon), although most timetables now use the 24-hour system |
Minute | 1/60 of an hour = 60 seconds |
Second | 1/60 of a minute |
Recurring intervals | |
Annual | Yearly |
Perennial | Year after year |
Bi-annual | Twice a year |
Bi-ennial | Every two years |
Bi-monthly | Every two months; twice a month |
Bi-weekly | Every 2 weeks; twice a week |
Diurnal | Daily (especially with temperature) |