This document is a white paper written by Richard Cassidy and Ben Wild. It commences by citing an essential reference: A handbook of dates for students of British history, new edition, revised by Michael Jones (RHS, London 2000). The book is a thorough review of regnal years, law terms, saints' days and the calculation of Easter, with calendars for every year.
This white paper provides a brief outline of that information and is an essential resource for understanding the dates mentioned in the Hungerford Cartulary and other early records.