Autumn/early winter of 2018, no way March.Is there a clue in 'Artifact instability'?
"A recent build also changed how the Artifact Power numbers increase or decrease once your Artifact is unstable. Now your Artifact will increase in Artifact Power until February 2nd, then the total Artifact Power displayed will decrease until March 2nd. On March 19 it will begin to increase very very rapidly. This effect is probably only visual and your actual Artifact Power may not change. "
The week of March 19 is 77 days post 7.3.5
That would be a lot sooner than most pundits are expecting it.