A calculation from today's inputs
A project finishes when all required work can finish. The scheduler considers remaining effort, assigned resources, working patterns, commitments, dependencies, release constraints and interruptions. It does not simply take the last stage number or copy a date from Monday.
Changing an assumption can change the date. Updating remaining effort after progress is therefore more useful than moving a date to somewhere comfortable.
Why this date now?
Select work on Timeline or open its forecast history. Why this date describes the current dependency chain, local constraints and resource gates. Collaboration may need two people at the same time; waiting work may need an external release.
An unable-to-forecast result is a real warning. Check resources, availability, prerequisites and release conditions rather than treating the missing date as zero delay.
What changed since last time?
The previous recorded forecast is an earlier meaningful observation, not necessarily yesterday's forecast. The current live forecast can be newer than the last recorded observation. Forecast history shows those separately; movement explains the changes around them.