Digital-Hero said:The time period from which the Chief came back to Earth from High Charity was not long. If you notice at the end of Halo 2 when Lord Hood says, "Master Chief can you tell me what you are doing on that ship?" The battle around the defense platforms was still happening. Unless Master Chief was on Truth's ship for weeks when it plummeted to earth, there really isn't much to explain away the time difference. The ODST's are probably still in the City as the Chief is going through the events of Halo 3.
I'm nerding out here, forgive me.
Halo: Uprising could provide the answer. It could have been weeks for all we know.
We learned in Halo 2 that Covenant cruisers can simply speed past the MAC platforms without getting hit if they want. I suspect that the Covenant would know that by the time the second invasion happens. They probably ignored the fleet and the MAC platforms in orbit and headed straight for the planet.