Hello @Vignesh_Kannan , if your parameter allows the user to enter any date for start and end period it is not possible to prevent them to enter dates that are not valid according to your business logic.
Here one option that you have is to create two calculated fields (one for each date) and then perform a validation using a calculated field, e.g.
validation:
ifelse(dateDiff(start_date, end_date ,"MM") >= 12, "Dates are invalid, please select a range of 12 months between startd and end date", "Dates are valid")
Then you can include this field in a insight visual for example and include it in you dashboard to provide feedback to your end users. You can select a Top computation with a maximum of 1 element like this:
Hope it helps, I am marking this question as solved to help other members in the community, if you still have any further questions please let us know.
Thank you for posting into the QS community!