Bug with 'fill' and 'dates'

[nfourcau]

When writing two cells with dates inside, and then selecting both and using the 'fill' function, I get the following dates with the same interval (measured in days). It seems to wokr well but it is only the display ! The real cell content (shown in the upper bar) is the first date for all cells and when I come back to the sheet, all dates are back to the first one.

Expected behavior : the use of the 'fill' function should also change the 'real' cell content with the displayed date.

Thx