How do I change from a fiscal year to a calendar year while using the turbo tax software program?

The default is a calendar year.  Unless you have already entered a Fiscal Year data in the 1040 Worksheet, under the section titled Personal Info, Filing Status, dependent info, you are good to go for a Calendar Year.
In case you need to change TO a Fiscal Year, right-click in the boxes in the section I just noted above, and you will be able to OVERRIDE the default setting (calendar years).  However, if you explore a little further, you will see that TurboTax does not support a Fiscal Year.  pk

FAIL!  The program does NOT allow a user to override the field on the Form1040 Worksheet (where that data arewa exists).  Right-click and/or Ctrl-D do NOT allow me to enter a different start and end date for my tax year!  Always '?USED to work but not this year (2019)