Problem in Auto Filling Dates in Excel

I suspect that the "dates" are not dates but text and hence excel is just incrementing the number at the end of the text string. For example if you go under number format and choose a different date format does it change the view of the cell to that new format? I'm guessing not. So you need to enter the dates in a format Excel recognizes as a date and then fill down (fyi it is also good to do 2 or 3 and then highlight them and drag down so excel can 'see' the pattern). Then you can use number formatting to display the dates the way you want. If that date format isn't available as a default you can use Custom Format to create it DD.MM.YYYY