This causes the table to be deleted in the database and a table labelled  table_name_tmp1 to be created which of course is empty.  Now this table does contain calculated fields and foreign keys and I wonder if that is why MVD is behaving as it is.

Another table that I made the same alteration to in the same database, accepts the alteration without deleting the table.

Is this expected behaviour by MVD?

Obviously SQLite itself doesn't know about date types and considers them to be text, so I think it strange that MVD should do what it appears to be doing.