Jan 1st, anon.
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.