Stardate 48481.2: The crew of Deep Space Nine proceed on the Defiant to Earth to attend a Starfleet symposium on the Gamma Quadrant. As Commander Sisko, Doctor Bashir, and Lieutenant Dax beam down, they are caught in a temporal fluxuation. They do make it to San Francisco, but they wind up there in the year 2024.
When the Cardassian occupation of Bajor ended in 2369, the mining space station Terok Nor was left abandoned, its systems ripped out. By invitation of the Bajoran provisional government, Starfleet stepped in to oversee the rebuilding and day-to-day operations of the newly christened Deep Space Nine.
The years of Starfleet's nonintervention into Cardassian matters, however, had taken its toll on relations with the Bajorans. Consequently, Starfleet's position was a tenuous one; many Bajorans, suspicious and hostile as a result of decades of Cardassian oppression and brutality, did not greet the Federation's presence with open arms. The Federation's assistance is put to the test as DS9 becomes a center of travel and commerce that stretches into the Gamma Quadrant.