BT (also B.T. or b.t.): Before Tranquillity. Any date before the first landing of Terragens on another celestial body, when the Apollo 11 mission achieved touchdown on the Old Earth's Moon. This was July 20, 1969 c.e. or AD in the Gregorian calendar, and Armstrong Day, 0 AT in the later Tranquility Calendar that became standard in Solsys during the Federation Age.
After Tranquility is a collection of 12 short stories set in the Orion's Arm Universe and includes a mix of works published in Voices: Future Tense - the OA ezine, and new works created especially for this collection.
It is currently available at Amazon in both paperback and Kindle versions.