How this calculator works
A Julian year is a fixed 365.25 days, which is 31,557,600 s. Astronomers use it so that a year is a constant when rates such as light-years are defined. A calendar year is 365 or 366 days, so it does not have a single length in seconds. Dividing seconds by 31,557,600 gives Julian years. For a calendar answer, work with the actual dates instead, or convert through days and then count the calendar years.
Formula
Julian years = seconds / 31557600. seconds = Julian years x 31557600. One day is 86,400 s and 31,557,600 s is 365.25 days.
Worked example
31,557,600 s = 1 Julian year. 86,400 s = 0.00273785 year. 604,800 s = 0.0191650 year. 31,536,000 s, which is 365 days, = 0.999316 year. 10 years = 315,576,000 s.
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Frequently asked questions
Why is a year 365.25 days on this page?
The Julian year averages the ordinary 365 day year with a leap day every four years, giving 365.25 days. It is the standard year for astronomy and for definitions such as the light-year.
How many seconds are in a calendar year?
A common year has 31,536,000 s and a leap year has 31,622,400 s. Neither equals the Julian year exactly, which is why calendar calculations need the actual dates.
How do I convert a specific age to seconds?
Count the calendar days between the two dates, then multiply by 86,400. Leap days and any clock changes have to be handled by the date arithmetic; a fixed year factor cannot capture them.
Is this the same year used in the light-year?
Yes. The light-year is the distance light travels in one Julian year of 31,557,600 s, so a duration in Julian years converts directly to the time part of that definition.