Some Project UDF fields have time stamps on date values
An immediate workaround is to put the string " date" (note the space) in the column title of any such field. This is case insensitive but the space is important: "( Date)" works but "(Date)" doesn't.
A second workaround is to export the sheet to Excel and apply a date format to the entire column in the exported workbook.
Finally, if the timestamps are in the database, a script can be written to clean them up.