Make sure you ignore any other calendar selections as I have here (Year=, Month=) if that is how you are selecting dates. If you are just selecting "OrderDate" then you don't have to worry about those other fields.
If your FY starts on other than month 1, change the "1" at the end to the month (eg 8).
I assume you are talking about filtering metrics expression based on the date .
In my case If I select input parameter Mar 2021, all data in dashboard should be filtered FYTD through March.
I have implemented an FYTD indicator in load script based on current date and it is working fine but there I cant change that YTD dynamically . It will always be based on current date. That means in my filter, if I select 2020 and 2021, it selects data till Mar 12th (todays date) for 2020 and 2021.