|Location of Event :
|Nature of Event :
||Past Incursion 
In 2371 Deep Space nine's senior officers visited Earth for a symposium on board the USS Defiant. Whilst in orbit a micro-singularity exploded near the ship; the energy of the detonation forced residual chroniton particles from the ship's cloaking device into a high state of polarisation. The chronitons redirected a transporter beam from the Defiant over three centuries into the past, sending Sisko, Dax and Bashir into San Francisco in the year 2024.
Quickly taken prisoner by a pair of policemen, Sisko and Bashir were placed in one of the 'Sanctuary Districts' common at the time. These areas were dumping grounds for the homeless, mentally ill or unemployed people were isolated from the rest of society. Dax, meanwhile, fared rather better and fell in with prominent media tycoon Chris Brynner.
Sisko quickly realised that the party had materialised shortly before the famous Bell Riots, a pivotal event in America's history which happened in the district he was now imprisoned in. Conditions in the districts had deteriorated so much that the residents seized hostages and demanded improvements. When police raided the district dozens of rioters were killed; but not one hostage was hurt thanks to the protection given to them by Gabriel Bell, leader of the rioters. Bell ultimately even sacrificed himself to save the hostages. The riots forced the USA to finally begin dealing with the social problems which had long plagued it.
Unfortunately, Bashir unwittingly caused Bell's death shortly before the riot by instigating a fight. The alteration to the timeline caused a drastic change in future history; with no impetus to deal with their social problems the USA spiralled downwards into chaos. Ultimately even the Federation itself ceased to exist, apart from the single exception of the USS Defiant which was protected by the same chroniton effect which had originally caused the problem.
Captain Sisko was forced to assume his identity of Bell in an attempt to correct the damage.  Meanwhile, the Defiant crew had determined four possible dates for the time jump, and set out to investigate each in turn.
Sisko managed to convince Webb, one of the rioters, to act as his representative, but Webb was cut off from media access when he tried to explain the situation in the sanctuary districts to the public. Fortunately Dax was able to convince Brynner to restore access and allow the rioters to make their case to the people. She then slipped into the district via the sewers and located her comrades.
Unmoved by the pleas of the rioters, the Governor send in troops. The riots ended as before, with most of the rioters killed. Sisko was wounded in the assault but survived; he and Bashir switched their ID cards with those of two dead men and convinced the former hostages to tell the real story of the riots before leaving when the Defiant crew finally tracked down the correct time window.
Thanks to Sisko the normal course of history was largely restored; the only real difference is that the history books now identify Gabriel Bell as a man who bears a remarkable resemblance to a certain Starfleet officer...