Definition:Time/Unit/Year
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Definition
The year is a derived unit of time.
\(\ds \) | \(\) | \(\ds 1\) | year | |||||||||||
\(\ds \) | \(\approx\) | \(\ds 365 \cdotp 24219 \, 878\) | days | |||||||||||
\(\ds \) | \(\approx\) | \(\ds 365 \cdotp 24219 \, 878 \times 24 \times 60 \times 60\) | seconds |
That is:
\(\ds \) | \(\) | \(\ds 1\) | year | |||||||||||
\(\ds \) | \(\approx\) | \(\ds 365\) | days, | |||||||||||
\(\ds \) | \(\) | \(\ds 5\) | hours, | |||||||||||
\(\ds \) | \(\) | \(\ds 48\) | minutes, and | |||||||||||
\(\ds \) | \(\) | \(\ds 45 \cdotp 9747\) | 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.
\(\ds \) | \(\) | \(\ds 1\) | calendar year | |||||||||||
\(\ds \) | \(=\) | \(\ds 12\) | months usually, depending on the calendar used | |||||||||||
\(\ds \) | \(=\) | \(\ds 365 \text{ or } 366\) | 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
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $365 \cdotp 2422$
- 1992: George F. Simmons: Calculus Gems ... (previous) ... (next): Chapter $\text {B}.25$: Kepler's Laws and Newton's Law of Gravitation
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $365 \cdotp 24219 \, 878$
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): year
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): year