Context: The 800th anniversary of the original charter occurred on 15 June 2015, and organisations and institutions planned celebratory events. The British Library brought together the four existing copies of the 1215 manuscript in February 2015 for a special exhibition. British artist Cornelia Parker was commissioned to create a new artwork, Magna Carta , which was shown at the British Library between May and July 2015. The artwork is a copy of an earlier version of this Wikipedia page , hand-embroidered by over 200 people. On 15 June 2015, a commemoration ceremony was conducted in Runnymede at the National Trust park, attended by British and American dignitaries. The copy held by Lincoln Cathedral was exhibited in the Library of Congress in Washington, D.C., from November 2014 until January 2015.  A new visitor centre at Lincoln Castle was opened for the anniversary. The Royal Mint released two commemorative two-pound coins. In 2014, Bury St Edmunds in Suffolk celebrated the 800th anniversary of the barons' Charter of Liberties, said to have been secretly agreed there in November 1214.

Question: What day was the original charter occur?

Answer:
--15