Use PREVIOUSYEAR function on a column that only contains a Year value

Hello,

I am trying to create a "Previous Year" measure using the PREVIOUSYEAR function but get the following error since my 'Fiscal Year' column is actually a Text data type. 

"A column specified in the call to function 'PREVIOUSYEAR' is not of type DATE. This is not supported."

Is there a work around for this?   Possibly creating a fake date format for the 'Fiscal Year' column?

Thanks.