If you have several dates listed in the sheet summary on a project, then you can have an option for those to be pulled onto the sheet summary report not in a row, but all in one column? Then you can sort by the date and it will actually make them go in order? Instead of a row of dates, it would be a sortable column of dates for one or more projects. Otherwise, if you try to sort it when there are several dates in a row then it does not sort correctly.
This type of sorting is possible in row reporting, since it pulls by row, but there is more chance for error because of people typing things wrong.