What did JRR Tolkien do as a 'day job' for over 30 years?

These were his day jobs:

In early 1917 he began work on what was to become The Silmarillion - his great work of language and mythology - whilst convalescing at Great Haywood. The Tale of Beren and Luthien Tinuviel always remained his favourite. Edith, he said, was his Luthien.

From 1918-20 he was an assistant on the Oxford English Dictionary.
In 1920, he became Reader in English language at Leeds University,
where he later held the Chair from 1924-5.
In 1926 he returned to Oxford as Professor of Anglo-Saxon
and later became Merton Professor of English (1945-59).
http://www.bbc.co.uk/history/programmes/centurions/tolkien/tolkbiog.shtml