Old Style (or O.S.) and New Style (or N.S.) are used in English language historical studies either to indicate that the start of the Julian year has been adjusted to start on 1 January (NS) even though contemporary documents use a different start of year (OS); or to indicate that a date conforms to the Julian calendar (OS), formerly in use in many countries, rather than the Gregorian calendar (NS). The internationally used Latin cognates of O.S.