He lived most of his life in Chislehurst, Kent, where, it is said, after riding his horse in Petts Wood near his home early one summer morning and noticing how many blinds were still down, the idea for daylight saving time first occurred to him.

Modern DST was first proposed by New Zealand entomologist George Vernon Hudson, although many publications incorrectly credit Willett.

Through vigorous campaigning, by 1908 Willett had managed to gain the support of a member of parliament (MP), Robert Pearce, who made several unsuccessful attempts to get it passed into law.

Germany had already introduced the scheme when the bill was finally passed in Britain on 17 May 1916 and the clocks were advanced by an hour on the following Sunday, 21 May, enacted as a wartime production-boosting device under the Defence of the Realm Act.

[9] William Willett married twice, firstly in 1879 to Maria Mills (died 1905), with whom he had seven children; secondly in 1910 to Florence Strickland, with whom he had one daughter.