1904 - Jim Corrigan is born.
1925 - 21-year-old Jim becomes a cop.
1929 - 25-year-old Jim is promoted to homicide detective.
1934 - 30-year-old Jim is killed by gangsters & becomes the Spectre's new human host. Madam Xanadu helps him understand his role.
1939 - WW2 begins.
1945 - WW2 ends.
1949 - The Spectre abandons Jim Corrigan's civilian identity.
1 year ago - The Spectre appears in the battle against Maggeddon.
The difficulty with the Spectre is that the power at his disposal is so vast, his existence basically breaks every story he's involved in. The Spectre is the embodiment of the Wrath of God. The idea is that it's only by having a human host that the Spectre is capable of empathy with the human condition. There have been some spectacular Spectre books, but contextualizing his entire history as a part of the DC universe as a whole provides a few unique challenges.
The trick seems to be to focus on his human existence as opposed to his divine one. The otherworldly entity is obviously immortal and unending, but his host, Jim Corrigan, had a life and a career with the Justice Society. It even helps contextualize his career as a superhero to imagine that it was Jim, not the Spectre, who was serving with the Justice Society, using the powers he wielded as the entity's host to become a hero. Then, after the war, when he feels his duty is completed, he abandons his false life as Corrigan to simply become the Spectre. From there, his appearances become fleeting glimpses of power experienced only in near dream states.
There is quite a bit of story we're leaving out regarding the host of the Spectre. Hal Jordan became the new host after his death, and then Gotham detective Crispus Allen. These stories aren't bad, but it cheapens the character to be so continually drawn into the affairs of mortals.