Convert Days to Years

About converting Days to Years

Days (d) and Years (yr) are both units of time, so converting between them is a single multiplication: multiply your Days figure by 0.002738. Ten Days comes to 0.02738 Years, and a hundred works out at 0.2738 Years.

Rule of thumb: going from Days to Years divides, so the figure always shrinks — it takes about 365.25 Days to make a single Year. If your answer came out bigger, you have the conversion the wrong way round.

What is a Day?

A day is exactly 86,400 seconds — and that is a statement about the unit, not about the Earth. A real solar day varies slightly depending on winds, tides and what the planet’s core is doing, and tidal friction is gradually lengthening it. The gap between the tidy unit and the untidy planet is what leap seconds patch over. Astronomers also distinguish the solar day from the sidereal day, one full rotation relative to the stars, which is about four minutes shorter because the Earth has meanwhile moved along its orbit.

What is a Year?

There is no single year. A Julian year is exactly 365.25 days; a Gregorian calendar year averages 365.2425 days, because its leap rule drops three leap days every four centuries; and the tropical year — the actual round trip of the seasons — is about 365.2422 days. The leap-year rules exist precisely to stop the calendar drifting away from that tropical figure. This converter uses the Julian year of 31,557,600 seconds, the convention astronomers use and the one the light-year is built on, but it is a chosen convention rather than a fact about the Earth.

To put both in perspective: a day is one turn of the Earth on its axis, while a year is one lap of the Earth around the Sun.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Years to Days converter, or browse all Time converters.