Years to Julian Years (yr to a)
1 year equals 0.9999794661 Julian years (rounded).
How to convert years to Julian years
To convert years to Julian years, multiply the number of years by 0.9999794661. The factor is rounded to 10 significant digits. To go the other way, multiply Julian years by 1.000020534 (rounded).
Julian years = years × 0.9999794661
Example: 10 years = 9.999794661 Julian years.
Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.
About these units
Year (yr)
The average Gregorian calendar year of 365.2425 days (31,556,952 seconds). A common year has 365 days and a leap year 366.
A year is the Earth's trip around the Sun, but there are several versions. The tropical year, which tracks the seasons, is about 365.2422 days. The sidereal year, measured against the stars, is about 365.2564 days, roughly 20 minutes longer, because the Earth's axis precesses. Calendars must squeeze these into whole days, which is the origin of leap years. English year descends from Old English gear, while Latin annus, the source of annual, comes from a different root.
The Gregorian calendar, introduced by Pope Gregory XIII's bull of 24 February 1582, fixed the problem of Julian drift that had moved the March equinox away from 21 March and upset the date of Easter. Ten days were skipped, so Thursday 4 October was followed by Friday 15 October. Its rule of skipping leap days in century years not divisible by 400 gives a mean year of 365.2425 days, the value this site uses for the year. Britain and its empire switched in 1752 and Russia in 1918. Scientists write the year as a, with the Julian year fixed at 31,557,600 seconds.
1 year = 31,556,952 seconds (exactly).
Sources: Wikipedia: Year; Wikipedia: Gregorian calendar
Julian Year (a)
Exactly 365.25 days (31,557,600 seconds). The astronomical standard; a light-year is defined using it.
Astronomers wanted a year that would never change, so they borrowed the average length of the old Julian calendar year: exactly 365.25 days of 86,400 SI seconds, or 31,557,600 seconds. The symbol is a, or aj when it must be told apart from other years. It is not an SI unit, but the IAU lists it among the non-SI units accepted for use in astronomy.
The mean tropical year drifts slightly from one year to the next, so it makes a poor unit, whereas the Julian year is constant because it rests on the SI second. It still approximates both the sidereal and tropical years to within about 0.008 days. The current standard epoch, J2000.0, is exactly 12:00 TT on 1 January 2000, and other Julian epochs are counted in Julian years from it. The light-year is defined as the distance light covers in one Julian year.
1 Julian year = 31,557,600 seconds (exactly).
Sources: Wikipedia: Julian year (astronomy); Wikipedia: Light-second; NIST SP 811 Appendix B.8: factors for units outside the SI
Related conversions
- Julian years to years (reverse)
- Years to seconds
- Years to minutes
- Years to hours
- Years to days
- Years to weeks
- Years to months
- Years to milliseconds
- Years to microseconds
- Years to nanoseconds
- Years to decades
- Years to centuries
- Years to millennia
- Seconds to Julian years
- Minutes to Julian years
- Hours to Julian years
- Days to Julian years
- Weeks to Julian years
- Months to Julian years
See all time units.