A census was taken to record those living in a household at midnight on a Sunday. The dates of the census varied from year to year. Sun/Mon. 6/7th June 1841 Sun/Mon. 30/31st March 1851 Sun/Mon. 7/8th April 1861 Sun/Mon. 2/3rd April 1871 Sun/Mon. 3/4th April 1881 Sun/Mon. 5/6th April 1891 Sun/Mon. 31st March / 1st April 1901 It may be of interest that the actual wording in the Population Act, issued on the 9th August 1850 is 'The census is to be taken on Monday, March 31, of all persons in houses on the previous night.......The Secretary of State is to adopt means to take an account of the number of houseless poor on the night of the 30th of March, and of persons travelling and on shipboard.' Apparently the date was changed to March (it was held in June 1841) because of the 1851 Great Exhibition which was to open on the 1st. of May, which was likely to fill London with many visitors during May and June. Regards Stan Mapstone www.mapstone.org