- 1944: The family moved to Bwlch Llan in Cardiganshire when he was seven years old, and John became fluent in Welsh.
- 1956: He went to study history at Cardiff University and graduated with first class honours.
- He won a scholarship to study for a doctorate at Trinity College, Cambridge.
- 1963: He was appointed to his first post in the History Department of Swansea University, to lecture through the medium of Welsh.
- 1973: He was appointed as a lecturer in the History Department of the University College of Wales, Aberystwyth.
- 1974: John was the first Warden of Pantycelyn Hall and stayed there until 1992.
- 1981: He was promoted to become a senior lecturer at the University College of Wales, Aberystwyth.
- 1990: His notable volume, 'Hanes Cymru' (A History of Wales) was published.
- 1998: During the Ron Davies sexuality affair, John, after consulting Janet his wife, decided to declare his own bisexuality in a television interview.
- John was one of the editors of The Welsh Academy 'Encyclopaedia of Wales'.
- 2020: He won The Welsh Book of the Year award for 'Cymru: Y 100 Lle i’w Gweld Cyn Marw' (Wales: 100 Places to See Before You Die).
- 2014: Published his autobiography 'Fy Hanes i' (My History).
‘John Davies was one of the most prominent historians of Wales. He started his career at Swansea University before moving to work at Aberystwyth University. He became the first warden of Pantycelyn, the Welsh halls of residence.’ – Y Lofla – https://www.ylolfa.com/authors/100/john-davies