Comment by danparsonson

It's a next-word-prediction-machine, not a calculator. It's not aware of the passage of time, or how long things take, and doesn't reason about anything. It's just very good at putting words together in combinations that look like answers to your inputs.

That's really useful for some tasks, like regurgitating code to perform a specific function, but it's basically useless for jobs like estimating schedules.