• Perpetual Calendar
• Heavy Green Marble and Brass
• Perpetual Calendar Covers 50 years from 2014 to 2063
• Height: 0.75 in. (2 cm)
• Diameter: 3 in. (7.5 cm)

A calendar which is good for a span of many years. An interesting instrument used by scientists and navigators in centuries past. Its origin goes back some 500 years. Actually one of the earliest calculating instruments invented. Not withstanding their name, Perpetual Calendars really only covered forty or fifty years, which was close to the actual life span in those times. Intriguing, also effective… calculate the day of the week for any given future date, within a 50-year span.