The year was 2761. It was 209 years since the Covenant attacked Reach and since humanity discovered the existence of Halo. The Covenant has not been seen or heard of for over two centuries. Some speculate they got deeply involved with the Flood and were killed. No one knows for sure.
The SPARTAN-II Project is old news. The SPARTAN-VI's are the new protectors of humanity and, of course, all remaining SPARTAN-V's. The Project is much more mature and suffers less deaths during training due to enhancements. There are 750 Spartans who graduated the Project, and it is said that the next program will graduate even more Spartans.
Earth is still occupied, but fear has lasted the two centuries that the Covenant will return and again try to take Earth. Humanity has moved throughout the rest of the galaxy and has 1,500 worlds occupied now. Earth has been restored to the way it was over 700 years ago. No mass cities covering entire countries; large cities, but larger, spanning open land. The tectonic plates have been wandering and Pangaea is the landmass of Earth.
Reach has not been tampered with. It is still glassed, but a large orbitary museum holds all the knowledge of the Covenant, the past of the SPARTAN Projects, and the story of the Pillar of Autumn's journey to Halo. Tour shuttles fly down above the planet every now and then.