Public holidays in Serbia:
January 1st and 2nd, New Year's Day
January 7th, Julian Orthodox Christmas
February 15th and 16th, Serbia National Day
Varies, Orthodox Good Friday
Varies, Orthodox Easter Monday
May 1st and 2nd, International Workers' Day
November 11th, Armistice Day
If one of the non-religious holidays falls on a Sunday, then the next working day is a non-working day.