Dated Jan. 16, 1865, Special Order No. 12, A&IGO, authorized organization of the 13th Georgia Cavalry Regiment to date from May 2, 1864.

No one could have known about the "official date" before January 16th of 1865. The official date was used to calculate pay of field and staff officers promoted or appointed to positions in the new regiment. It served no other purpose.

To my knowledge full companies were not detached, but there were detachments that would have been out of touch.