Old Style (O.S.) and New Style (N.S.) indicate dating systems before and after a calendar change, respectively. Usually, this is the change from the Julian calendar to the Gregorian calendar as enacted in various European countries between 1582 and the 20th century.
In England, Wales, Ireland and Britain's American colonies, there were two calendar changes, both in 1752. The first adjusted the start of a new year from Lady Day (25 March) to 1 January (which Scotland had done from 1600), while the second discarded the Julian calendar in favour of the Gregorian calendar, removing 11 days from the September 1752 calendar to do so. To accommodate the two calendar changes, writers used dual dating to identify a given day by giving its date according to both styles of dating.
For countries such as Russia where no start of year adjustment took place, O.S. and N.S. simply indicate the Julian and Gregorian dating systems. Many Eastern Orthodox countries continue to use the older Julian calendar for religious purposes.
1917Oct, 25
Old Style date of the October Revolution in Russia
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Events on 1917
- 22Jan
Woodrow Wilson
World War I: President Woodrow Wilson of the still-neutral United States calls for "peace without victory" in Europe. - 15Mar
Nicholas II of Russia
Tsar Nicholas II of Russia abdicates the Russian throne ending the 304-year Romanov dynasty. - 2Apr
Woodrow Wilson
World War I: United States President Woodrow Wilson asks the U.S. Congress for a declaration of war on Germany. - 5Jun
Conscription
World War I: Conscription begins in the United States as "Army registration day". - 27Jul
Battle of Passchendaele
The Allies reach the Yser Canal at the Battle of Passchendaele.