Why is estimating hard? 1. You haven't done it before. Not exactly the same thing. You think you've done it before, but you haven't. If you had actually done it before, you would probably be faster this time, not slower. 2. Other things besides you have changed, or will change. Coworkers, company, customers, tools, economic realities, the weather. Either it's already changed, or it's going to change. That has an impa…
I have a story about the boss: years ago the boss walks over to me and describes a straightforward change with priority that it should start right away. I said it was a two or three day job and that considering testing and other internal process could be confidently delivered in two weeks. "That's too long, never mind". I then overhear him asking a coworker about the same project. He says: "Easy, that is a two or thr…
So I'd say "2 weeks to complete end to end".
The other guy would say "I'll crank it out this afternoon". Other guy would deliver code that wouldn't run, and then require 3 weeks from me, QA, and him to actually massage into something that works the right way.
So instead of 2 person-weeks, it would take like ~5-6 person-weeks all in. Great stuff.