Hi @Mark Jerrom
Do you mean you want to format the date parameter as "dd-mm-yyyy"? It doesn't seem very easy.
I did a simple test, whether it is modifying the language of the report or modifying the settings of the computer region, the date parameter always maintains the "mm-dd-yyyy" format. In the end, only one method worked, that is, the rendering format of the date parameter will only change after the browser language is modified.
Of course it's just a format change, I select the date in the calendar control and it still renders the data correctly, but if you manually enter an incorrect date format it will give you the same error.
For more details, you can refer to this link: https://stackoverflow.com/questions/29775170/i-want-datetime-parameter-in-ddmmyyyy-format-in-ssrs-report.
Best regards,
Aniya