When the delivery date is set before the project even starts, planning "forward" isn't enough. Backward scheduling (rétroplanning) starts from the end and works back to today — revealing whether the deadline is actually achievable.
A classic project plan starts from today and moves forward task by task toward an estimated end date. Backward scheduling does the opposite: the delivery date is fixed and non-negotiable (an event, a legal deadline, a client due date), and you work backward in time to place every task relative to that deadline.
The value is surfacing a problem early: if the backward schedule places a task before today's date, the requested deadline is simply unrealistic given the current scope — better to know that 60 days out than 5 days out.
The event date, the legal deadline, or the contractual delivery date — the anchor point for the whole calculation.
What's the very last task before delivery? Then the one before that, and so on — the reverse of a classic work breakdown structure.
Position each task working backward from the target date, accounting for dependencies between them.
If the first task of the backward schedule lands before today, the deadline isn't achievable as-is: cut scope, add resources, or renegotiate the date.
Tip: once the backward schedule is validated, it converts directly into a regular Gantt chart for day-to-day tracking — backward scheduling is for scoping, the Gantt is for running it.
Product launch, trade show, conference: the date doesn't move, everything else gets organized around it.
Compliance with a fixed legal deadline, with no room to negotiate.
A client contract with late-delivery penalties makes the delivery date non-negotiable.
A submission deadline set by a public buyer never shifts.
See also the general definition of a schedule in project management (Wikipedia), and guidance from the PMI and the APM on deadline-constrained planning.
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