I do not think you can do it with a query as you have coded it.?
Normally there would be the dates themselves in the table and then you specify the start and end.
As it stands now, you just have the range of dates in the table you are trying to append from.?
INSERT INTO tblDate ( TheDate )
FROM tblDate, Table1
WHERE (((tblDate.TheDate) Between [Table1].[StartDate] And [Table1].[EndDate]));
The experts will know a better way. In fact didn't TheDBguy offer a method?