Time Converter

There are exactly 86,400 seconds in a day. This is calculated as 24 hours × 60 minutes × 60 seconds = 86,400 seconds. This is a fixed value used universally in timekeeping.

Earth takes approximately 365.2422 days to orbit the Sun. We round to 365 days for a regular year, and add a leap day every 4 years (with exceptions for centuries) to account for the extra ~0.25 days. This is why we use 365.25 as an average year length.

A nanosecond is one billionth (10⁻⁹) of a second. Light travels approximately 30 centimeters (about 1 foot) in one nanosecond. Computer processors execute operations in nanoseconds — a modern CPU can perform billions of operations per second.

There are exactly 1,000 milliseconds in one second. Milliseconds are commonly used in computing, sports timing, and scientific measurements. Human reaction time averages about 200-300 milliseconds.

A fortnight is a period of 14 days (two weeks). The word comes from Old English "fēowertyne niht" meaning "fourteen nights." It's commonly used in British English, Australian English, and in some pay schedules (fortnightly pay).

A decade is 10 years, while a century is 100 years (10 decades). A millennium is 1,000 years (10 centuries). These terms are commonly used in history, demographics, and long-term planning. The 21st century began on January 1, 2001.