Recommended Time Maintenance Book Series

[Solitaire1]

I'm currently reading a DC Comics series called "Booster Gold." Booster Gold is a disgraced superhero who now has the mission to keep time and history intact by ensuring that no one significantly changes the past. Due to the nature of his mission, no one can know what Booster Gold is actually doing and he must let the world think of him as nothing more than disgrace and/or a joke.

As an example: he undid Robin's (Dick Grayson's) death in the early days of the New Teen Titans, ensured Jonathan Kent was born in Smallville by preventing the murder of the doctor who would deliver him, and ensured that Hal Jordan became a Green Lantern by causing the other eligible candidate (Guy Gardner) to be on the other side of the country.

What I was wonder is if there are any book series featuring individuals/groups with the same type of mission?

Thanks in advance.