THEODOSIANI LIBRI XVI CUM CONSTITUTIONIBUS SIRMONDIANIS
The Theodosian Code has been composed between AD 429 and 438. In 429 the Emperor Theodosius ordered for the nine men commision to compose all imperial constitutions issuing from the time of Constantine. Together with the Codex Hermogenianus and Codex Gregorianus this collection had to be an actual law book and a model for teaching of jurists. The collection of the using constitutions had to be add of answers (responsa) and juridical tractates. Thus it would be unified together leges and ius vetus. There is nothing known of a result of this commision's work. The new commission of sixteen men with the questor of sacred palace Antiochus was made in 435. After two years working the comission made sixteen books of laws. Not all of them were left to us in all the volume. The most part of the first six books is lost.
Codex Theodosianus received an official status together with the Codex Hermogenianus and Codex Gregorianus which befire had only character of the private collections. The Codex got in force 15 February 438 at the Ost Roman Empire and 1 January 439 at the West Empire. There are 2529 imperial issues from Constantine to Theodosius II in it. The earliest constitution in the Codex is CTh.13,10,2 of 1 Juny 311 and the latest is CTh.6,23,4 of 16 March 437.
More detailed see the article 'Theodosian Code' (Smith's Dictionary)