Old Style and New Style dates
Old Style (O.S.) and New Style (N.S.) indicate dating systems before and after a calendar change, respectively. Usually, they refer to the change from the Julian calendar to the Gregorian calendar as enacted in various European countries between 1582 and 1923.
Memorial plaque to John Etty in All Saints' Church, North Street, York, recording his date of death as "28 of Jan: 170+8/9"
William Hogarth painting: Humours of an Election (c. 1755), which is the main source misinterpreted for "Give us our Eleven Days".
Thomas Jefferson's tombstone. Written below the epitaph is "Born April 2. 1743. O.S. Died July 4. 1826."
Issue 9198 of The London Gazette, covering the calendar change in Great Britain. The issue spans the changeover; the date heading reads: "From Tuesday September 1, O.S. to Saturday September 16, N.S. 1752".
The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year. The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts of Oriental Orthodoxy as well as by the Amazigh people.
The Tusculum portrait of Julius Caesar
Russian icon of the Theophany (the baptism of Jesus by John the Baptist) (6 January), the highest-ranked feast which occurs on the fixed cycle of the Eastern Orthodox liturgical calendar