Do you need your data to be stored in a table or would a timetable be acceptable instead? Offhand I can't think of anything you can do with a table that you can't also do with a timetable, though the reverse is not true.
If you're not tied to storing your data in a table, convert it to a timetable using table2timetable. Once you've done that you can use a datetime as a row index, or you can use timerange or withtol if you're concerned that the dates and times in the RowTimes property of your timetable include fractional seconds that may not be shown in the display. See this documentation page for examples of these techniques.
