1913 - Jay Garrick is born on his family's farm.
1919 - 6-year-old Jay's father returns from world war one with a Greek helmet.
1933 - 20-year-old Jay goes to college to study chemistry.
1936 - 23-year-old Jay is caught in a lab accident and gains his speed force powers & becomes the Flash.
1939 - WW2 begins.
1945 - WW2 ends.
11 years ago - 38-year-old Jay returns from Ragnarok with a few surviving members of the Justice Society, his connection to the speed force depleted.
While most of the Classic Justice Society loses their life when they are lost in Ragnarok, a few members of the team have business back in the regular timeline. Jay is an important mentor to the modern Flash, and having him survive is very important.
One distinction we made, however, was that it's not specifically necessary for Jay to maintain his powers. He's a far more compelling character as a font of experience rather than as another in a large group of speedsters. Even his role as the adopted guardian of Bart Allen doesn't require him to have any powers.
It's the sacrifice of his speed force connection that allows the Justice Society to escape Ragnarok. The result of this change in the story is that Jay is a much younger character, barely 50 years old, which means that he'll be able to provide the young heroes he mentors with sage advice for a long time to come.