Definition:Time/Unit/Year
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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
- 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): Entry: year
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): Entry: year