Thank you for the provided steps.
I tested the described behavior on my end with the 2020.1 218 version of our dlls, however I was not able to reproduce the same result. That is why I am attaching the sample project, which I used for testing. May I ask you to check it out and let me know, if I am missing something? If possible, you can modify it and send it back. This will hopefully allow me to investigate further and better assist you.
As for the format of the dates, you can change the application's culture to the desired one and set needed format. Additionally, you would have to set the IsLocalizationLanguageRespected property to False on the RadGridView inside the dialog. I have demonstrated this approach in the shared sample project.
I am looking forward to your reply.
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