Calendar year definition
/What is a Calendar Year?
A calendar year is a twelve-month period that begins on January 1 and ends on December 31. It is based on the Gregorian calendar, and is used in most countries to plan social and business events. The calendar year is the basis for numerous tax filings. It tends to be the default fiscal year for entities that have not specifically established a different date range for their fiscal years.
The Leap Year Cycle
Every four years, an extra day is added to February to account for the approximately 365.25 days Earth takes to orbit the Sun. This makes the year 366 days long in a leap year.