Convert Second to Year (s → yr)

Converting seconds to years is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in seconds

   Start with the number of seconds (s) you want to convert.
2. 2
   Multiply by 3.169 × 10^-8

   The conversion factor from s to yr is 3.169 × 10^-8. Multiply your value by this number.
3. 3
   Read the result in years

   The result is your value in years (yr).

Multiply the value in seconds by 3.169 × 10^-8. For the reverse direction, multiply by 31,557,600.

• ✓60 s = 1 minute; 3600 s = 1 hour; 86,400 s = 1 day.
• ✓For sub-second intervals use ms (milliseconds), µs (microseconds) and ns (nanoseconds).
• ✓The symbol is s (lowercase). "sec" is informal.

• ✗Writing S instead of s for the second.
• ✗Confusing second of time with second of arc in astronomy.
• ✗Assuming microsecond and millisecond are similar — 1 ms = 1000 µs.

What is the Second?

The second is the base SI unit of time. Since 1967, it has been defined by atomic physics: the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom. This makes the second extraordinarily reproducible — modern atomic clocks based on optical transitions can keep time to a few parts in 10¹⁸. The second is the foundation of all time measurements: the minute (60 s), the hour (3,600 s), the day (86,400 s). It is also fundamental in physics — speeds (m/s), accelerations (m/s²), frequencies (Hz = 1/s), and Planck's constant all reference the second. International civil time, GPS, and the internet's time synchronization all depend on cesium-based atomic seconds. The second relates to the millisecond (1,000 ms = 1 s), the microsecond, and the nanosecond.

• Everyday timekeeping
• Scientific and engineering measurements
• Sports timing (100 m sprint in ~10 s)

What is the Year?

The year equals exactly 365.25 days (the Julian year used in astronomy) — the time for Earth to complete one orbit around the Sun. The Gregorian civil year averages 365.2425 days, achieved through the leap-year rule (every 4 years, except centuries not divisible by 400). The year is the fundamental unit for age, contracts, education, taxation, and astronomical calculation. The 'sidereal year' (Earth's orbit relative to fixed stars) is slightly longer at 365.256 days, while the 'tropical year' (relative to the seasons) is 365.2422 days. The year relates to the day (365.25 days), the month (12 months), and the second (about 31.557 million s). Light-year calculations use the Julian year of exactly 365.25 days. Earth's orbital period has been almost perfectly stable for millions of years, making it a reliable timekeeping reference.

• Age, anniversaries and legal tenure
• Interest rate calculations
• Astronomy and science