Day was born in Mobile, Alabama, and raised in Poplarville, Mississippi, by his mother Jeanne Bass Day. Jeanne was widowed at the age of 28 when Glen was approximately 2 years of age. His grandfather Glyndol Bass, was young Glen’s primary male role model. Bass, an avid golfer and member at Pearl River Valley Country Club just outside Poplarville, started Glen playing golf when he was 2 to 3 years of age. By the age of 10, he held a 5 handicap and was able to regularly shoot par on 18 holes. He graduated from Poplarville High School in 1983, attended the University of Oklahoma, then turned professional in 1988. He has one sister, Danielle, and is married to the former Jennifer Ralston. They have two daughters, Whitney Elizabeth, born in 1994 and Francis Christina, born in 1996.