Date calculations with c# in asp.net web forms

I'm using c# in a asp.net web forms page.

The fiscal year period runs from July 1 to June 30 of the next year.

For example FiscalYear 2017, is the period from 07/01/2016 to 06/30/2017

For example FiscalYear 2016, is the period from 07/01/2015 to 06/30/2016

On my page I'm going to have a asp Textbox and a asp button

What I want is, I'm going to type a date in the Textbox and then when I click the button , on the same page I want it to display a message saying what fiscal year that date is in.

So for example, if I type this date in the Textbox  08/23/2015 and then I press the button, the message on the page will say
"The date you entered is in FiscalYear 2016"

So for example, if I type this date in the Textbox  02/12/2014 and then I press the button, the message on the page will say
"The date you entered is in FiscalYear 2014"

Any ideas of what I do with the date entered in the Textbox in order to find what fiscal year it is in?
That's the part I'm having trouble with.