The date format in your sample project is correct. And I have found the difference.
I have dragged&dropped the date attributes in to page which caused them to be reference selectors. And I do not know why, but as a reference selector, date format is not as expected.
But when I have first added date pickers into the page and then drop the date attributes in it, it is in correct format.
Thanks for the sample project which made me got the point.
Are there multiple languages and which language is assigned to the user you use for testing?
Please find the requested screenshots attached.
Thanks in advance.