Old Style (O.S.) and New Style (N.S.) are sometimes used with dates to indicate whether the From the 12th century to 1752, the civil or legal year in England began on 25 on 9 December 1582 (O.S.) so the next day was 20 December 1582 (N.S.). .. 4 (Revised ed.). Cambridge: Cambridge University Press. pp. 17–20.