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.