TheNationalDayisadesignateddateonwhichcelebrationsmarkthenationhoodofacountry.OftentheNationalDaywillbeanationalholiday.
TheNationalDayisoftentakenasthedateonwhichastateorterritoryachievedindependence.Otherdatessuchasthecountry'spatronsaintday,orasignificanthistoricdatearesometimesused.MostcountrieshaveasingleNationalDayperyear,thoughafew,forexample,IndiaandPakistan,havemorethanone.Besidesthat,eachofthetwospecialadministrativeregionsofthePeople'sRepublicofChina,namelyHongKongandMacao,celebratethedayoftheestablishmentofthespecialadministrativeregion,aswellastheNationalDayofthePeople'sRepublicofChina.
TheimportanceattachedtotheNationalDay,andthedegreetowhichitiscelebrated,varyenormouslyfromcountrytocountry.InFrance,forexample,NationalDayis14JulyandisknownasBastilleDay.ItiswidelycelebratedandtheFrenchTricolourismuchinevidence,whilethePresidentoftheRepublicattendsamilitaryparadeontheChamps-ÉlyséesofParis.IntheUnitedStates,theFourthofJulycelebrationsarewidelycelebratedwithfireworksandbarbecues.IntheRepublicofIreland,St.Patrick'sDay,March17,hasbeentheNationalDayandaPublicHolidayformanyyears,andinrecentyearsithasbeenobservedasafullPublicHolidayinNorthernIrelandtoo.However,intherestoftheUnitedKingdomtheconstituentcountries'patronsaints'daysarelow-keyaffairs.
MostcountrieshaveafixeddateNationalDay,butsomehavemovabledates.AnexamplehereisJamaica,whichcelebratesitsNationalDayonthefirstMondayinAugust.ThiscommemoratesindependencefromtheUnitedKingdomwhichwasattainedonMonday,6August1962-thefirstMondayinAugustofthatyear.AnotherexampleisThailandwhichcelebratesthebirthdayoftheKingon5December.Thisdatewillchangeontheaccessionoftheheirtothethrone.