Hi,

You can create a edit validate rule to validate the format of the date and include it in the advanced tab of the property rule under Use Validate. 

You can refer to the OOTB edit validate rules for a reference.

Regards,

Gisela

To add to Gisela's suggestion, You can validate the format at the property level using Edit-Validate rule. As a sample please check
NotFutureDate:  Expects a string in theValue in the format YYYYMMDD. This rule returns true if that date is today's date or a past date, or false if the date is a future date or not in the expected format.

Hope this helps.

Best Regards,

Mounika

More on this : https://pdn.pega.com/community/pega-product-support/question/how-allow-user-input-date-format-mmddyyyy

Best Regards,

Mounika

This is a candidate for client side validation since you want to enforce a particular syntax. Edit validate is the ideal way to achieve this.

May I also know the reason behind making it a String property. Date type property would have handled this automatically.

Dear All

I missed one point. Actually the user updates the data in excel in character format and we are using MSOParseExcelFile to populate the excel data to Clipboard. I need to perform date validation on the clipboard to make sure tha value that the user entered is in YYYYMMDD format.