Baseline

What gets frozen

The plan as approved is photographed whole: scope (the WBS structure and weights) and schedule (each task's planned start and finish), with cost plans included where formal EVM is practiced. Immutability is the defining property. The current plan gets edited daily; the baseline stays exactly as it looked at the moment of approval. That is what gives the question "how far behind plan are we?" a fixed reference — where "plan" means the plan approved that day, not the plan as of now. In practice, snapshots are cut at contract signing, kickoff, or right after a major approved change — and past baselines are kept as history, useful for tracing how the plan itself has drifted.

Why it matters

Without a baseline, delays disappear. On a project that revises its plan weekly to match reality, no task is ever late — the reference itself chases the actuals. The baseline is the source of planned value (PV), the comparison line drawn beside current bars on the Gantt, and the grounds on which "we are three weeks behind" is even a meaningful sentence. In acceptance and contracts, an approved baseline is the line of defense in disputes.

Common misconceptions

Swapping baselines frequently is the first misconception: a re-baseline is a formal event that passes through change control, not makeup applied at every slip. Move the reference often enough and measurement goes numb. The opposite extreme fails too: clinging to a stale baseline after a major approved scope change turns every variance from that point into noise rather than signal, and buries the real ones. When an approved change affects the baseline, formally update the affected baseline — and state in reports which baseline the numbers are measured against.