It is believed that Isaac's ancestors had come out from England and settled around the Pennsylvania area.  They were among the other United Empire Loyalists who came up to Canada around the time of the United States separating from Great Britain in 1776 and they settled in Ontario in the Orillia area around the shore of  Lake Dalrymple..  Apparently they all took pie shaped lots radiating out from the lake and Isaac likely continued farming in that area.

What is known for sure is that Isaac Day married Mary McNabb and they had two sons; Joel and Duncan, and three daughters; Lodice, Isabella (Belle) and Calista.  Joel married a Lizzie Ramsay and they had at least three children; Mary, Alma, and Kenneth.  It is also known that Joel's daughter Mary married a McMullen, but it is not known if she or any of her siblings had any children.  No information is currently known about Isaac's girls Lodice and Calista.  

Duncan settled in Manitoba and married Jennie (Atkinson) McLaren and Belle also went to Manitoba where she married Robert Atkinson, who happened to be a nephew of Jennie's.  Duncan and Jennie had three sons, Cecil, Bruce and Arnott, as well as Jennie's son Rob McLaren from her previous marriage.  Rob McLaren and his wife Elsie had two children Joyce and Alex.  Cecil and his wife Elsie had one son Lloyd and three daughters, Vivian, Marge and Marion.  Bruce and his wife Greta had two daughters Doreen and Leona and one son Barry.  Arnott and his wife Dorothy had two sons Bill and Murray and one daughter Janice.  

Rob and Belle Atkinson had three daughters that survived infancy, Calista, Wanda and Mary.  Calista and her husband Jim Brown had seven children, Gwenda, Penny, Judy, Jackie, Bob, Tom and Lois.  Click here for their family tree.  Wanda and her husband Ken Fraser had four children, Iona, Eugene, Juletta and Melenie.  Click here for their family tree.  Mary married later in life to Bob Pierce and they did not have any children.  With the illness and subsequent early death of Jennie, her sons Cecil, Bruce and Arnott spend a lot of their time at their Aunt Belle and Uncle Rob's farm.  The Atkinson sisters became the sisters the Day boys never had.