Companies are managed based on a 12-month fiscal year, usually starting on the first day of a calendar quarter (January 1, April 1, July 1, or October 1). The name given to a fiscal year is the calendar year of the last day of the last month of the fiscal year.
So, for example,
If your fiscal year starts on January 1, the fiscal year is the same as the calendar year.
If your fiscal year starts on April 1, the fiscal year that begins on April 1, 2017 is called FY2018 because the last day of that fiscal year (April 1, 2017 to March 21, 2018) is in calendar year 2018.