Put a date in, say, cell A1 - format the cell how you would like to
see it.

Then in A2 put this formula:

=A1+1

The next day's date should appear in A2, and it should have picked up
the format from A1 (if not, then format A2 the same as A1 or use the
Format Painter icon).

Then copy this cell down column A as far as you would like.

Hope this helps.

Pete

And when you don't want to use formulas, but enter consequtive dates
manually, then:

a)
Enter starting two dates into column/row, then select both of them, and drag
to range you want the array of dates to enter. The date interval, you
entered with 2 starting entries, will be preserved. And Excel differs days,
months, and years. An example:

01.05.2008; 02.05.2008 :  03.05.2008; 04.05.2008; ...
01.06.2008; 11.06.2008 :  21.06.2008; 01.07.2008; ...
01.01.2008; 01.05.2008 :  01.09.2008; 01.01.2009; ...
01.01.2008; 01.01.2009 :  01.01.2010; 01.01.2011; ...

Or b)
Enter a date into cell and activate it. Now you can use the Fill feature
from menu Edit>Fill>Series with data type set to date. You can determine
ending value, date unit, and filling direction.

"Why am I forced to exchange data in excel format?"
Truly forced?  Possibly (I know my company is).  Perhaps because it is a de
facto standard for many businesses and for U.S. Federal Government?  You want
to do business with them, you respond with the required files in the required
format.

"Am I going to have to make what I am trying to make on my Linux?
Probably..."  Possibly, may be easier for you in the short run - but again,
compatibility with external organizations may suffer greatly.

Just keep asking away here in these forums, and we'll keep trying to help as
much as possible.  For the time being, probably the "New Users" group would
be a good place for your questions; people won't make too many assumptions
about your knowledge of Excel or skills with it and will patiently try to
assist as much as possible.