Change the Length of your Financial Year

In case you want to adjust the length of a particular financial year, go to Settings - Accounting - Financial Year. Under Existing Financial Years click on the arrow next to the financial year for which you want to adjust the length. 

A field will pop up where you can fill in the new start and end date of the financial year.
If previous years exist already, you can only fill in a new end date. Afterwards, click on Save.