Time Converter

What time measures

Time measures the duration of events and their order. The SI base unit is the second (s), defined through the number of oscillations of radiation from the caesium-133 atom: 9,192,631,770 periods per second.

Main units and where they are used

• Millisecond (ms) – computer networks and electronics.
• Second, minute (60 s), hour (3600 s) – everyday time and work planning.
• Day (24 h = 86,400 s) and week (7 days) – the calendar.
• Month and year – calendar units whose length is not entirely constant.

Common pitfalls

The biggest mistake is assuming a month is always the same length: it has 28 to 31 days, so converters normally use an average such as about 30.44 days. A year is usually counted as 365 days, though the average is about 365.25 because every fourth year is a leap year. Another trap is turning time into decimals: 1.5 hours is 1 h 30 min, not 1 h 50 min; 0.25 h = 15 min.