Without having test data which are wrong sorted it's impossible to help you. Just save XML data returned from '/ajax.asp' and include the data in your post.
You should include datefmt:”m/d/Y” in the column model which corresponds your date format. Corresponds to the documentation default value is the ISO Date (Y-m-d). Moreover I don't recomend you to use a large int value instead like rowNum:10000.
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