A perpetual calendar in brass for determining the dates of Easter in the Julian and the Gregorian calendar. Signed "Hartston Fecit", English, 18th century

Record summary

Held and catalogued by Science Museum Group, London (object number 1990-304), this is a perpetual calendar, made in England, dated 1700–1799. The Atlas places it in the Early Modern Horology period (1600 – 1750) of its Instruments collection. The record is illustrated with 3 photographs.

Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.

Catalogue description

The source record does not include a narrative description. The structured fields above are reproduced from it.

Atlas type guide

Scientific and navigational instruments

Timekeeping has always been tied to astronomy, navigation and measurement. Observatories used transit instruments to determine the exact moment a star crossed the meridian, and set their regulators by it; navigators combined sextant observations with chronometers to find longitude; surveyors, engineers and physicians used counters, pedometers and timers derived from watch and clock technology.

Instruments in this collection show how time measurement supported science and everyday technical life. Their makers were often the same workshops that produced clocks and watches, and their scales and dials document changing units and standards.

General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.