Definition:Time/Unit/Year

From ProofWiki
< Definition:Time‎ | Unit(Redirected from Definition:Year)
Jump to navigation Jump to search

Definition

The year is a derived unit of time.

\(\displaystyle \) \(\) \(\displaystyle 1\) year
\(\displaystyle \) \(\approx\) \(\displaystyle 365 \cdotp 24219 \, 878\) days
\(\displaystyle \) \(\approx\) \(\displaystyle 365 \cdotp 24219 \, 878 \times 24 \times 60 \times 60\) seconds


That is:

\(\displaystyle \) \(\) \(\displaystyle 1\) year
\(\displaystyle \) \(\approx\) \(\displaystyle 365\) days,
\(\displaystyle \) \(\) \(\displaystyle 5\) hours,
\(\displaystyle \) \(\) \(\displaystyle 48\) minutes, and
\(\displaystyle \) \(\) \(\displaystyle 45 \cdotp 9747\) seconds


It is defined to be equal to the orbital period of Earth round the sun.


Calendar Year

A calendar year is the number of days between dates with the same designation in adjacent years.

As a year is not an integral number of days, it is necessarily an approximation to the actual year.


\(\displaystyle \) \(\) \(\displaystyle 1\) calendar year
\(\displaystyle \) \(=\) \(\displaystyle 12\) months usually, depending on the calendar used
\(\displaystyle \) \(=\) \(\displaystyle 365 \text{ or } 366\) days, usually, but it depends on the calendar used


Symbol

The symbol for the year is $\mathrm {yr}$ or $\mathrm y$.

In some scientific contexts $\mathrm a$ (for annus, Latin for year) is used.


Also known as

The year as defined here is also known as a tropical year to distinguish it from the various other types of year.


Also see

There are others.


Sources