December is the twelfth and last month of the Human year.
Shannon O'Donnell first arrived in Portage Creek, Indiana on December 27, 2000. (VOY: "11:59")
The Vulcan ship Seleya was pulled into the Delphic Expanse in December of 2152, with all contact subsequently being lost. (ENT: "The Expanse")
In late December of 2152, an Orion freighter was scheduled to rendezvous with the ECS Horizon, however the Horizon failed to make the transfer. (ENT: "Horizon")
In December of 2153, the Andorian warship Kumari entered the Delphic Expanse in search of the Earth starship Enterprise NX-01. (ENT: "Proving Ground")
The Enterprise NX-01 rescued an alien from a massive spatial anomaly in the Delphic Expanse on December 27, 2153. (ENT: "Harbinger")
In December of 2154, the Enterprise NX-01 encountered an Orion trader named Harrad-Sar. (ENT: "Bound")
In December of 2370, Miles O'Brien was arrested by Cardassian forces and put on trial for allegedly supplying weapons to the Maquis. (DS9: "Tribunal")
The events in the novel Traitor Winds took place in December of 2270.
Some of the events in the novels Worlds of Star Trek: Deep Space Nine, Volume 1 and Worlds of Star Trek: Deep Space Nine, Volume 3 took place in December of 2376.
Many of the events in the novel Articles of the Federation took place in December of 2380.
According to the Millennium trilogy of novels, a combined Borg/Federation fleet arrived at the Guardian of Forever's planet on December 22nd, 2399 to find it was interdicted by hostile Grigari forces; on December 28th, Kathryn Janeway and an army of Federation troops made it to the surface, only to be destroyed by a singularity bomb.