Time conversions

time conversions
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Select a unit of time

What is time?

Definition: Time is a measurable interval during which something happens, exists or acts in apparently irreversible succession. The base unit of time in the International System of Units (SI) is the second (s). Other measurable intervals that have long been used as units of time include milliseconds (ms), minutes (min), hours (h), days (d), weeks (w), months (mo), years (yr), centuries, etc. Although these are non-SI units of time, they are officially accepted to be used along with other SI units.

Time is relative to the system of reference from which the measurement is made.

Common time conversions

  • 1 second = 1,000 milliseconds
  • 1 minute = 60 seconds = 60,000 milliseconds
  • 1 hour = 60 minutes = 3,600 seconds
  • 1 day = 24 hours = 1,440 minutes = 86,400 seconds
  • 1 month = 4 weeks
  • 1 week = 7 days (5 working days + 2 weekend days) = 168 hours = 10,080 minutes
  • 1 year = 12 months = 365 days
  • 1 leap year = 12 months = 366 days
  • 1 decade = 10 years
  • 1 century = 10 decades = 100 years
  • 1 millennium = 10 centuries = 100 decades = 1,000 years
  • Age of the Universe = about 13.5 billions of years since big-bang, for an observer on Earth
  • Age of our Galaxy (Milky Way) = approximately 8.8 billions of years, for an observer on Earth
  • Age of the Earth = nearly 5 billions of years, for an observer on Earth

Subdivisions and multiples of the second using SI prefixes

Subdivisions of the second Multiples of the second
Name Symbol Value Name Symbol Value
decisecond ds 10-1 s decasecond das 101 s
centisecond cs 10-2 s hectosecond hs 102 s
millisecond ms 10-3 s kilosecond ks 103 s
microsecond ?s 10-6 s megasecond Ms 106 s
nanosecond ns 10-9 s gigasecond Gs 109 s
picosecond ps 10-12 s terasecond Ts 1012 s
femtosecond fs 10-15 s petasecond Ps 1015 s
attosecond as 10-18 s exasecond Es 1018 s
zeptosecond zs 10-21 s zettasecond Zs 1021 s
yoctosecond ys 10-24 s yottasecond Ys 1024 s