Atlas took delivery from CIT Leasing in Jan 2016
The freighter conversion was done in April 2017. Presumably, the AD would have been done then.
7 Jan. 2016 N258CT Atlas Air
5 April 2016 N631GT Atlas Air
8 Dec 2016 N1217A Atlas Air
April 2017 N1217A Atlas AirBCF (cargo) conversion
30 Apr 2017 N1217A Amazon Prime Air operated by Atlas