You can start this week ... The federal government uses a fiscal year from Oct. 1 to Sept. 30, so companies doing a lot of business with the government may adopt a similar fiscal calendar.

A 52-53-week tax year is a fiscal tax year that varies from 52 to 53 weeks but does not have to end on the last day of a month." A calendar year, on the other hand, is defined as "12 consecutive ...