The perpetual calendar mounted on the covers of an aide-mémoire illustrated and described by both Baptiste (p. 139, item 171) and Turner (p. 155 and p. 161, item 320) seems to have some similarities with the present example: whilst some of the information differs (e.g. lengths of night and day in February), and the decoration differs, the basic format of the two dials and the information given are alike. Baptiste dates the calendar as 18th century, whilst Turner suggests a late 17th/early 18th century dating. As the style of the letters on the present example seems slightly cruder and earlier than that on the aide-mémoire, a mid- to late-17th century dating could be possible.