Definition of Calendar Year
A calendar year is the 12 consecutive months from January through December. In other words, it is the 365 days (366 days in a leap year) beginning on January 1 and ending on December 31.
Example of Calendar Years
In the U.S., individuals file their personal income tax returns based on the calendar year of January 1 through December 31. Many U.S. corporations also have accounting and income tax years that coincide with the calendar year of January 1 through December 31. However, U.S. corporations may have an accounting year and income tax year that is not a calendar year.
Examples of Non-calendar Years
If a U.S. corporation has a non-calendar accounting year, it is referred to as a fiscal year.
An example is a U.S. retailer whose financial statements report the amounts for the fiscal year covering the 52-week period of Sunday, February 4, 2018 through Saturday, February 3, 2019.
Often educational institutions have fiscal years that begin on July 1 and end on the following June 30.