The 1 January 2020 implementation date was confirmed by IMO in October 2016, giving certainty to refineries, bunkering and shipping sectors.
http://www.imo.org/en/MediaCentre/WhatsNew/Pages/default.aspx
The new lower 0.50% limit on sulphur in ships’ fuel oil will be in force from 1 January 2020, under IMO’s MARPOL treaty, with benefits for the environment and human health. This was the message delivered to the Asia Pacific Petroleum Conference (APPEC) (24-26 September) by IMO’s Edmund Hughes....
http://www.allaboutshipping.co.uk/2018/09/25/imo-sulphur-2020-limit-no-delay/