# Definition:Time/Unit/Year

(Redirected from Definition:Year)

## 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.