Timeline Splinter

The Federation Department of Temporal Investigations classifies Temporal Fractures or "Timeline Splinters" are alternate timelines created by attempts to meddle in temporal affairs by irreparably changing the timeline.

First Splinter Timeline

In the year 2373, the Borg made an attempt to send a Borg sphere to Earth's past using a chronometric vortex, after losing their Borg cube in the Battle of Sector 001. The Enterprise-E immediately followed, and were taken afloat in the sphere's temporal wake. While in the temporal wake, they saw the final effect of the Borg's tampering with history — the Earth of the Borg timeline, completely assimilated. The Enterprise followed the sphere into the past and succeeded in saving their own history.

However, for the time that the temporal vortex existed, the Borg on the assimilated Earth could observe the Enterprise, just as the Enterprise crew had observed the results of the Borg timeline. When the Enterprise re-opened the vortex to return home, the Borg devised a plan to strike out at the Enterprise using a temporal weapon of their own. The Borg weapon had no discernible effect on the Enterprise's return home, but the resulting temporal incursion fractured the fabric of space and time, creating an parallel, unstable timeline called the First Splinter. This was later referred to as the ODE — the original divergence event.

At first, the two timelines were identical, except for the inherent instability of the First Great Splinter. Every subsequent incidence of time travel and other temporal disruption caused additional divergences and "splinters" to form. One of the major divergences was the reaction in the prime timeline to the discovery of instability in the Romulan system's star, which led to Jean-Luc Picard being promoted to admiral by Fleet Admiral Victor Bordson to command the evacuation of Romulan space aboard the USS Verity. In the First Splinter timeline, Picard remained in command of the Enterprise-E at the rank of captain, and Akaar was the C-in-C of Starfleet, not Bordson.

Second Splinter Timeline

The Second Great Splinter occurred in 2377, when Reman Praetor Shinzon assumes control of the Romulan Senate with the assistance of military hardliners within the Tal Shiar and Romulan High Command two years earlier than in the Prime Timeline - an incident still under investigation by the DTI. They launch attacks against the war-weakened Federation and Klingon Empires, prompting the start of the First Federation/Romulan War.

Behind The Scenes

The Splintered timeline concept was introduced in the closing installment of "Coda, Oblivion's Gate". The establishment of this timeline branching from the closing scenes of First Contact was intended to retroactively encompass the continuity of all crossover-oriented Pocket Books prose taking place after the finales of the respective series—the so-called "relaunches" of TNG, DS9 and VOY and tie-ins to various spinoff series, including New Frontier, SCE, Titan and Prometheus.

Federation Space has added to this idea, by creating a second splinter which places the RPG in an entirely different timeline to established canon (Lower Decks and Picard), and the "Beta-canon" novel series.