I always assume these type of "threats" are heavy handed suggestions for unpaid overtime. If you're telling him 2 months, and you assume a 40 hour work week, m

I always assume these type of "threats" are heavy handed suggestions for unpaid overtime. If you're telling him 2 months, and you assume a 40 hour work week, maybe he expects you'll work 120 weeks and get it done roughly on time? Its also possible that the manager has no idea what the scope of work is, has a different view of the scope of work is than you do, or in extreme\hostile situations thinks you're taking advantage and being lazy ("if only my reports would work harder!"), which also sounds like wanting forced unpaid overtime unless your productivity is unusually low.