I need to exclude the some holidays (ie Christmas and some additional days) form the standard calendar. Is it possible?

Yes you can. 

1. go to the "Calendar"

2. double click on the calendar name

3, select the date (i.e. 25 Dec is Christmas)

4. click "Clear" next to "Working time" 

repeat step 3 & 4 for all the dates you want to mark as public holiday, click "Save"

Thanks, Kartika, this was a great help. :-)