The easiest way to define a Public Holiday calendar for your country (or more than one country!) is to create a new calendar in the admin account, then share it to all users of the domain, as readonly.

Then simply import the appropriate public holiday calendar definitiion in iCal format, by importing the appropriate ics file into Desknow, selecting 'Folder/Import from iCal' from the menu.

You can find iCal files for the public holidays of most countries at the following address:

http://www.mozilla.org/projects/calendar/holidays.html

Simply copy the link for the calendar you're interested in, and paste it in the browser address bar, replacing webcal with http. Then download the ics file, and import it into DeskNow.