The "Pillars of Time" perpetual Gregorian calendar is a unique and collectable piece from France, designed to assist in calculating the day of birth within the era of 1600-2299. This innovative calendar offers a convenient way to calculate the day of week for any date between 1600-2299, making it a novel addition to any collection of ephemera or historical memorabilia. Its intricate design make it a prized possession for those interested in calendars and timekeeping.