January 1, 2019
https://www.whitehouse.gov/presidential-actions/2018-amendments-manual-courts-martial-united-states/
Justice Act of 2016 (MJA), division E of the National Defense Authorization Act for Fiscal Year 2017, Public Law 114-328, 130 Stat. 2000, 2967 (2016), except as otherwise provided by the MJA or this order, the MJA shall take effect on January 1, 2019.
(b) Nothing in the MJA shall be construed to make punishable any act done or omitted prior to January 1, 2019, that was not punishable when done or omitted.
(c) Nothing in title LX of the MJA shall be construed to invalidate the prosecution of any offense committed before January 1, 2019. The maximum punishment for an offense committed before January 1, 2019, shall not exceed the maximum punishment in effect at the time of the commission of such offense.
(d) Nothing in the MJA shall be construed to invalidate any nonjudicial punishment proceeding, restraint, investigation, referral of charges, trial in which arraignment occurred, or other action begun prior to January 1, 2019. Except as otherwise provided in this order, the MJA shall not apply in any case in which charges are referred to trial by court-martial before January 1, 2019. Except as otherwise provided in this order, proceedings in any such case shall be held in the same manner and with the same effect as if the MJA had not been enacted.