I just wanted that dates should behave like, well, dates.
Excel should take them as dates and I should be able to change their format.
And I've been able to solve much (I'll say around 70%) part of the problem.
My problem was that I was often in the habit of typing dates with dots in between the days and months and years (like 15.11.14), but excel won't accept them as dates unless I replace the dots with hyphens of the like. But I found that if I replace the hyphens or slashes with dots in the OS date format (in the Control Panel> Regional Settings), excel starts doing what I wanted. Even if I put dot in the first part in Regional Settings (like: dd.MMM-yy), even that did the trick.
Thank you very much for being with me.