Discovery, design, build, test, and release braided through overlap and review gatesUpdates with every input
Date & Time
Project Deadline Timeline Calculator
Construct a five-phase deadline timeline with controlled discovery-to-design and design-to-build overlap, external review lag, contingency, and a clear critical completion path.
Fully serial duration—
Duration saved by overlap—
Active phase path—
External review lag—
Contingency reserve—
Protected elapsed duration—
Longest phase—
Parallelization efficiency—
Interlocking phase ribbon
Discovery, design, build, test, and release braided through overlap and review gates
Phase ribbons share horizontal space where overlap is permitted, then pass through an external review gate and contingency reserve.
Phase timing ledger
Start, finish, overlap, and dependency timing by project phase
Audit every phase's baseline duration, overlap allowance, start offset, finish offset, and critical-path contribution.
| Phase | Duration | Overlap allowed | Start day | Finish day | Dependency | Critical contribution |
|---|
Timeline setup
Overlap only work that can truly proceed on stable inputs
- Estimate each phase independently.
- Limit early design to stable discovery outputs.
- Limit early build to approved design slices.
- Keep external review as a separate gate.
- Protect the resulting path with contingency.
Network logic
Overlap saves time only where predecessor uncertainty is controlled
Subtracting overlap from every phase creates fictitious parallelism and hides rework exposure.
The ribbon shows exactly which phases coexist, while the review gate and contingency remain distinct from productive work.
Calculation method
Calculate phase starts from predecessor completion less approved overlap
Only discovery-to-design and design-to-build overlap. Test waits for build, external review follows test, and release follows the gate. Contingency protects the active path.
Detailed calculation process and general formulas
Start_design=Finish_discovery-o_a DesignStart_build=Finish_design-o_b BuildFinish_test=Finish_build+TestBase=Finish_release+LProtected=Base(1+c)Symbols, meanings, and units
- o_a
- design overlap sharedecimal
- o_b
- build overlap sharedecimal
- L
- external review lagdays
- c
- critical-path contingencydecimal
- Protected
- planned completion offsetdays
Path diagnostics
Understand where elapsed time is created and recovered
The model separates serial duration, approved concurrency, external waiting, and protected reserve.
Serial baseline
—Sum of phase durations before overlap.
Concurrency gain
—Days removed by the two approved overlaps.
External gate
—Waiting time outside the active phase work.
Protected finish
—Elapsed path after contingency.
Decision takeaway: Treat overlap as a controlled dependency decision, not a percentage discount applied to the whole schedule.
Network checks
Validate the phase handoffs
- Overlapped work may generate rework.
- Test readiness can depend on full build completion.
- External review may repeat.
- Release windows can be calendar-constrained.
Timeline evidence
Artifacts that support the phase model
- Work breakdown structure
- Dependency map
- Design and build entry criteria
- External review service level
- Release checklist
Practical applications
Decisions this calculator is designed to support
Digital product delivery
Design begins on approved discovery slices and build begins on approved components.
What the result clarifies: The ribbon shows real concurrency without pretending test can start early.
Capital project approval
A delivery sequence includes a fixed external review before release.
What the result clarifies: The gate remains visible rather than being buried inside a phase estimate.
Worked example
Current-input substitution and reconciliation
Model limitations
The timeline is deterministic and assumes single-pass phases. It excludes iteration loops, resource leveling, calendar holidays, probabilistic risk, skill-specific capacity, and multiple branching dependency paths.
Project Deadline Timeline Calculator FAQ
Why are only two overlaps modeled?
They are the entered predecessor-successor relationships; later phases remain conservative.
Does review lag consume labor?
No. It extends elapsed time as an external gate.
Where is contingency applied?
To the active completion path after overlap and review lag.
Can the result replace a full project schedule?
No. It is a high-level critical-path planning model.