Plan Schedule Management produces the Schedule Management Plan — a component of the Project Management Plan that defines the scheduling methodology (CPM, critical chain, Agile iterations), the scheduling tool to be used, the level of accuracy required in duration estimates, the units of measure (hours, days, weeks), the thresholds that will trigger schedule variance reporting, and the rules for determining schedule progress (0/100, 50/50, physical % complete etc.).

This process happens early in planning, before any activities are defined or sequenced. It sets the rules that all subsequent schedule management processes follow. Without a Schedule Management Plan, different team members may use inconsistent approaches to estimating, sequencing and tracking — creating a schedule that is internally inconsistent and unreliable as a management tool.

Key decisions made in this process include: whether the project will use a time-scaled network diagram (Gantt chart) or activity-on-node (AON) notation, how change requests affecting the schedule baseline will be handled, and the frequency and format of schedule performance reporting.

Define Activities decomposes work packages from the WBS into individual activities — the smallest schedulable units of work that can be estimated, sequenced, resourced and tracked. The distinction between a work package and an activity is important: a work package is a deliverable-oriented grouping of project work from the WBS; an activity is a specific action that must be taken to produce that deliverable. A single work package may decompose into multiple activities.

For example: WBS work package "Install database server" → Activities: "Procure server hardware", "Configure operating system", "Install database software", "Configure database parameters", "Conduct acceptance testing". Each activity is then individually sequenced, estimated and assigned.

Rolling wave planning is explicitly accommodated in this process: activities for near-term work are defined in detail while activities for future phases are defined at a higher level, to be progressively elaborated as the project advances. This is particularly relevant in Agile and hybrid environments where future scope is not fully defined.

Sequence Activities creates the project network diagram — the logical map of how activities relate to one another. Every activity (except the very first and very last) must have at least one predecessor and one successor. The output is a Precedence Diagramming Method (PDM) network that becomes the foundation for Critical Path Method analysis.

The four types of logical dependencies (PDM relationships):

• Finish-to-Start (FS) — the most common: Successor cannot start until the predecessor finishes. "Testing cannot start until development finishes."
• Finish-to-Finish (FF): Successor cannot finish until the predecessor finishes. "Documentation cannot finish until testing finishes."
• Start-to-Start (SS): Successor cannot start until the predecessor starts. "Training materials development cannot start until training design starts."
• Start-to-Finish (SF) — the rarest: Successor cannot finish until the predecessor starts. Rarely used in practice.

Leads and lags are applied to dependency relationships to model real-world overlap or mandatory waiting periods. A lead is negative lag — it allows the successor to start before the predecessor finishes (overlap). A lag adds waiting time after a dependency is met before the successor can begin (e.g., a 3-day curing lag after concrete is poured). Leads and lags are adjustable parameters, not constraints.

Estimate Activity Durations assigns a time value to each activity in the activity list. Duration estimates are based on the work content of the activity, the resources assigned, and any calendar constraints (holidays, resource availability windows, working hours). Estimates are expressed in work periods (days, weeks) rather than elapsed calendar time — a 5-day duration estimate with a 5-day working week equals exactly one calendar week, but a 5-day estimate with holidays or part-time resources takes longer in calendar terms.

Key estimation techniques for duration:

• Analogous estimating: Uses duration data from similar past activities. Fast but less accurate. Best for early estimates or when detailed information is unavailable.
• Parametric estimating: Uses statistical relationships (lines of code per day, square metres per crew-day). Accurate for repeatable, measurable work.
• Three-point estimating (PERT): Triangular: (O + M + P) / 3. Beta/PERT: (O + 4M + P) / 6. Produces a weighted duration estimate that accounts for uncertainty. Also used to calculate standard deviation: σ = (P − O) / 6, which is used in schedule risk analysis.
• Bottom-up estimating: Estimates smaller components and aggregates. Most accurate when scope is well-defined.
• Reserve analysis: Adds schedule contingency reserves (buffer time) for identified risks and unknown unknowns. Schedule reserves are part of the schedule baseline.

Elapsed time vs effort: A 40-hour task assigned to one full-time resource takes 5 working days (elapsed time). The same task split between two half-time resources still takes 5 working days. Doubling the resources does not halve the duration unless the work is perfectly parallelisable — most activities have coordination overhead that reduces the efficiency of additional resources (Brooks' Law).

Develop Schedule is the most analytically complex process in Schedule Management — it takes the network diagram, duration estimates and resource information produced by the preceding processes and applies scheduling algorithms to calculate the schedule model. The primary output is the Schedule Baseline — the approved version of the schedule model against which actual performance is measured — and the Project Schedule, which shows planned start and finish dates for each activity.

The critical path method (CPM), resource levelling and schedule compression are the primary analytical tools used in this process. The schedule model is rarely correct on the first pass: the initial draft typically produces a project end date later than required, necessitating compression techniques or scope negotiation before the baseline can be established.

Schedule network analysis involves forward pass (calculating Early Start and Early Finish for each activity), backward pass (calculating Late Start and Late Finish), and float calculation (the amount of scheduling flexibility each activity has). Activities with zero float are on the critical path and cannot be delayed without delaying the project end date.

Control Schedule runs continuously from execution through project close. It has three distinct functions: monitoring actual progress against the schedule baseline, analysing variances and their impact on the project end date, and managing changes to the schedule baseline through integrated change control. Like Control Costs, Control Schedule is about management action — not just reporting.

The primary analytical tool is Schedule Variance (SV = EV − PV) and Schedule Performance Index (SPI = EV/PV) from Earned Value Management, which provide objective, cost-denominated schedule performance measures. Trend analysis (is SPI improving or deteriorating over time?), critical path analysis (has the critical path changed due to recent delays?), and what-if scenario analysis (what is the impact of this risk materialising?) are also used.

An important limitation of SPI: As a project approaches completion, SPI artificially trends toward 1.0 regardless of actual schedule performance — because EV approaches BAC regardless of whether work is late. This is why critical path analysis remains the primary schedule control tool even when EVM is in use. A project can have SPI = 0.9 but still be on critical path because the late activities have float.