William and Sarah Day are listed with their children in Portland Street, St Michales, St Albans, in the 1881 census - as another correspondent has told you. William is also listed in the 1851 census with his parents William and Sophia - and his widowed mother Sophia turns out to be living a few doors away from him in 1881.

I have posted full details (including links to web pages on the relevant sources, and to the places mentioned) on the web site "Genealogy in Hertfordshire" at www.hertfordshire-genealogy.co.uk as it is difficult to post tables and links on this site.