By the power of truth, I, while living, have conquered the universe.
Is it such a difficult concept to wrap your head about? Did anyone listen to the Audio Logs? seriously, Sadie's Story is one of the best things that happened to Halo and nobody seems to have listened to it.
The Legendary Ending depicts Truth observing the Covenant's excavation of the Portal Artefact for the first time, it's right next to Vigil's data centre where Dr Endesha detected the "seismic activity". You'll notice that the Epilogue is set "1 month after the drop".
[Edited on 05.10.2011 2:27 PM PDT]