Dates in the fifteenth century are difficult to reconcile with modern calendars: see Barker 2015, pp. 226–228 for the way the date of the battle was established. Barker, Juliet (2015) [2005]. Agincourt: The King, the Campaign, the Battle [US title: Agincourt: Henry V and the Battle that Made England] (revised and updated ed.). London: Abacus. ISBN978-0-349-11918-2.