Calendrical Volvelle

[Church of England]. The Book of Common Prayer.
London: John Sturt, 1717. (AFB9093)

This all-engraved edition of the Book of Common Prayer features a volvelle, or rotating circular table, that allowed the user to determine the dates of all the moveable Sunday feasts, such as Easter, during a particular year. For example, if New Year’s Day falls on a Thursday, as it did in 2015, then according to the volvelle the first Sunday after Epiphany in that year will be January 11, and Easter will be celebrated on April 5.