Lawrence Alexander Day[1] (born 1 February 1949 in Kitchener, Ontario) is a Canadian chess player, author, and journalist who holds the FIDE title of International Master.
As a youth in Ottawa, Day came under the influence of Fedor Bohatirchuk, a strong Ukrainian International Master and doctor, who had emigrated to Canada after the Second World War.
The highly experienced Bohatirchuk, who had a 3–0 score against Mikhail Botvinnik (later World Champion) exerted a very strong influence on Day's playing style.
Day played board three for Canada (scoring +7,=1,-2) on the bronze medal team at the World Students' Chess Olympiad, Mayagüez 1971.
He graduated from Carleton University in 1972 with a degree in English Literature, worked for the magazine Chess Canada for a time, and then became a professional player.
During his peak years, his use of the Modern Defence placed him near the leading edge of world research there; he developed the Pterodactyl Variation and used it with success against strong players.
He wrote a booklet on The Big Clamp opening system and co-authored a 1982 book on the Grand Prix Sicilian line with English Grandmaster Julian Hodgson.
He wrote a book about the life and games of the late Canadian International Master Bryon Nickoloff (1956–2004), a close friend, published in 2007 by Chess'n Math Association.