I worked with a non-technical manager (banking background, somehow wormed his way into managing development) who never asked devs what they thought a task would

I worked with a non-technical manager (banking background, somehow wormed his way into managing development) who never asked devs what they thought a task would take. I finally convinced him that this could not possibly work. I sat with him the first time he asked a dev how long the current task would take. The dev said "4 weeks". This guy said "I think it should take 2, so that is what I am putting in the schedule". Mind you, this guy had never written a line of code and had NO basis for his "thought" on the task length.