Remove the aliens, and you have a fair description of "The Day Before Forever" by Keith Laumer.
Steve Dravek awakens in a strange place with hazy memories just a few days before his one-hundred-and-sixty-second birthday. He quickly learns that he has been frozen for quite some time by Eternity, Incorporated (ETORP) which effectively controls society in this brave new world of 2103.
Slowly his memories return. Turns out his old workplace is now an ETORP preserve. In typical Laumer-hero fashion, he stages a clandestine attack on the facility, finding his old office -- and more clues, including some which appear to have been written by a previous version of himself! Each incarnation of Steve Dravek gets further in their investigation. Will he ever reach the end? Stay tuned. :-)
This story is available in the collection "Future Imperfect", the cover of which is based on a scene in the story. This collection was published by Baen and is available on one of the Baen Free Library CDs which means you can find it online if you look hard enough. Enjoy!