Might be easier to do things the other way around. In the condition for the filter for your repeating table from SharePoint, set the condition to be if the date time field from SharePoint is equal to and then use a formula with the translate function -- the first field would be your date time from your form, the second would the string "T" with quotes around it, and the third would be quotes with a space like this " ". That would compare your SharePoint data to the form field with the T replaced with a space.