Case for perpetual calendar

1822-1869 in St Bartholomew's Hospital

Buy this image as a print 

License this image for commercial use at Science and Society Picture Library

Science Museum Group
© The Board of Trustees of the Science Museum

Case for perpetual calendar, for calculating time of parturition, wood and ivory, in leather case, by Ferguson of London, 1822-1869

A Perpetual calendar calculates the time of parturition (childbirth) if the date of conception is known. This example is made of wood and ivory. The central disc is rotated to move the calendar with respect to the outer scale. The outer wheel is divided into four labeled parts: Conception, Quickening (movement or foetal activity), Foetus Viable (weeks 25-28), and Parturition (birth). The calendar was manufactured by Ferguson of London. It was used at St. Bartholomew’s Hospital, London. An expected due date (EDD) is after a full 40 weeks of pregnancy. Predicting an EDD is not an exact science. However, it is common to give birth between 38-42 weeks of pregnancy. Doctors now use ultrasound scanning to assess foetal development and estimate due dates.


Obstetrics, Gynaecology & Contraception
Object Number:
felt and leather
overall (no case): 14 mm 118 mm, .1kg
case for perpetual calendar
  • visual and verbal communication
  • calendar
Loan, Wellcome Trust

Cite this page


We encourage the use and reuse of our collection data.

Data in the title, made, maker and details fields are released under Creative Commons Zero

Descriptions and all other text content are licensed under a Creative Commons Attribution 4.0 licence

Using our data


Download catalogue entry as json

View manifest in IIIF viewer

Add to Animal Crossing Art Generator

Download manifest IIIF

Our records are constantly being enhanced and improved, but please note that we cannot guarantee the accuracy of any information shown on this website.