Subtracting 1 year from a single Parameter that prompts for a date range

I have a single parameter that prompts the user for a date range.

I can display the values from the prompt, but I'd also like to display the values for the same period one year in the past.

For instance if the user enters 1/1/2014 to 5/30/2014 I want to display 1/1/2013 to 5/30/2013.

Thanks for the help.

W