Hi Mike,
Thanks for bringing this issue to our notice.
I have created a Bug Report for this issue and here is the link for the same.
Defect #3032 - ValueChanged event triggers twice when isNullDate is True.As per your suggestion, I have created a Feature Request for having a separate change event for isNullDate property.
Feature Request #1365 - Add a separate Change event for isNullDate Property.Thanks for your interest in Syncfusion Products.
Regards,
Purusothaman.R