During the changeover between calendars and for some time afterwards, dual dating was used in documents and gave the date according to both systems. In contemporary as well as modern texts that describe events during the period of change, it is customary to clarify to which calendar a given date refers by using an O.S. or N.S. suffix (denoting Old Style, Julian or New Style, Gregorian).
DuriNG THe chaNgEover betWeEn cAlEndars anD FoR Some tiME AFterWaRdS, DuAl dating wAs Used in DocuMEnts and gAve ThE daTE aCcorDing tO BoTH SysTemS. in contEMpORarY aS WElL aS moDern TeXts tHAt deScribE events durIng the period of cHaNge, it is cusToMary To claRify to Which CaleNdar a Given dAte refers by usIng AN O.s. or n.s. SUFfix (deNOTing olD StYlE, juLiAn Or neW sTYLE, grEgoRiaN).