How to expand a conditional format over the entire cells range?

I want to change the background colour of a few cells based on weekday type – one colour for ‘normal’ weekdays and another colour for weekend.

I defined a conditional formula for one cell and specified there a range for (hopefully) the other cells I want to behave the same.

Something works, but not everything:
• one problem is that it works only for the cell where I defined first the formula;
• other problem is that I don’t understand why other cells in range always have the bg colour as defined in the formula;
• other problem is that some of the cells in range stays with the bg colour defined separately, as normal bg, given that I set that bg manually for all cells in range.

I created a test file:
https://www.secarica.ro/test/test_lo_conditional.ods
and this is what I see visually (in case a different locale may display something else):

Note: the week starts with Monday.

What is wrong (or possible incomplete) on what I did ?

If you want a CF based on ONE cell only, then you must use ABSOLUTE cell reference - at least for the row reference:
test_lo_conditional_based on one cell.ods (13.6 KB)

Right, now I understand all the mysteries I had. Thank you.