Be aware of accruals. For example, the year ended on December 31st. An accrual was entered on December 31st, then reversed on January 1st. If the new fiscal year ends on December 29th the accrual will be lost.
If each period end ends on the last day of a month you can still have an issue. For example: An accrual is entered on December 31st and reversed on January 1st. The new fiscal year is October 1st to September 30th. The accruals made on December 31st are now in the 3rd month of the new year, and those reversed on January 1st are now in the 4th month of the new year.