Most planning tools will happily tell you when you will reach a goal. Almost none of them will tell you the truth, which is that there are two answers and the distance between them is the only interesting number.
The two forecasts
The realistic forecast uses what you have actually done. Your real consistency, your real income, your real rate of finishing things. It is built from behaviour, not intention, and it is usually further away than you would like.
The ideal forecast uses near-perfect execution. Every session completed, every week clean, nothing dropped.
Every system I have used shows one or the other. The optimistic ones show you the ideal and call it a plan, which is how you end up eighteen months behind a timeline you never had a chance of hitting. The pessimistic ones show you the realistic number and quietly teach you that ambition is a character flaw.
Both are useless alone. The number that matters is the gap.
Why the gap is the product
Say the realistic forecast puts a goal at thirty-one months and the ideal puts it at nineteen. The gap is twelve months.
That figure does something neither forecast does on its own: it prices the behaviour. Twelve months is what the current inconsistency costs, stated in the only currency that is genuinely scarce.
And once it is priced, it becomes a decision rather than a guilt. Sometimes twelve months is worth closing and you change something. Sometimes twelve months is the correct price for a life that also contains other things, and the honest move is to accept the realistic number and stop pretending. Both are fine. What is not fine is not knowing which one you picked.
Where the gap comes from
A single aggregate number would be useless — "you are 38% consistent" tells you nothing you can act on. The gap has to decompose.
It is almost never evenly distributed. Most of it usually sits in one or two places: a task class you reliably avoid, a prerequisite you keep deferring, or a goal whose gate you have not noticed is a gate. The system's job is to point at the specific thing generating most of the difference, not to report an average.
That is the difference between a dashboard and a diagnosis.
What this rules out
It rules out a system that only knows your tasks. To forecast at all, it has to know costs, prerequisites, durations, skill requirements and what unlocks what — the dependency graph, not the list.
It also rules out the system lying to make you feel better. If the realistic number is bad, the realistic number is bad. Softening it would destroy the only thing the forecast is for.
A system that flatters you is not a system. It is company.