Definition:Leap Year

Definition

The number of days in a year is not an integer, but lies somewhere between $365$ and $366$.

However, it is convenient to assign an integer number of days to any given year.

It is also desirable to ensure that a particular day of the year occurs at approximately the same time each year.

In the Julian and Gregorian calendars:

some years are assigned $365$ days

and:

some years are assigned $366$ days.

The years which have $366$ days are called leap years.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $365 \cdotp 2422$
• 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