Architecture & practice·Estimation and planning
the date went on a customer contract, and after that the scope was the only thing left to move.
Commitment
A promise to deliver something by a time, made deliberately and with consequences for missing it. A commitment should be derived from an estimate with buffer, made by whoever owns the tradeoffs, and it should be far rarer than estimates are. Keeping the words distinct is one of the highest-leverage things an engineer can do in a planning conversation, because once an estimate has been repeated as a commitment it is very hard to take back.