Purpose and scope
What this timeline establishes
Calculate successor timing from dependency relationship, duration, lead, or lag. The result is designed to answer the planning question directly while preserving the assumptions needed to reproduce it.
Instructions
How to use this calculator
Enter predecessor start and duration, relationship type, signed lead or lag, and successor duration.
- Replace every example value with information from the schedule, agreement, journey, or system being modeled.
- Calculate and read the headline together with the supporting metrics. The visual output exposes sequencing that a single number can hide.
- Change one uncertain assumption at a time and compare the result before making a commitment.
Calculation
Method used
The predecessor finish is calculated first. The selected finish-to-start, start-to-start, finish-to-finish, or start-to-finish relationship anchors the successor.
The browser performs the calculation locally. No entered schedule or date information is submitted to CalcZero.
Calculation method last reviewed: June 20, 2026.
Worked scenario
Example calculation
Use the example to check the direction and scale of your own result. If the output differs sharply from a reasonable estimate, recheck units, offsets, inclusivity, and any value that crosses midnight.
Interpretation
Interpreting the calculated date and buffers
The result models one dependency pair. Negative lag represents lead time and can create intentional overlap.
- Save the input assumptions with any result shared outside the page.
- Read the full date and time whenever the calculation can cross midnight, a weekend, or a time-zone boundary.
- Use the visual schedule to locate handoffs, buffers, gaps, or deadline risk.
Visual audit
Reading the deadline timeline
The timeline is ordered from the triggering event through warnings, buffers, and the final modeled date. A buffer is deliberately different from the governing deadline: it creates time to review or act before the consequence date. When several rules might apply, calculate each scenario and keep the earliest defensible action date rather than averaging conflicting results.
Boundaries
Important edge cases and limitations
Business calendars, partial completion, multiple predecessors, resource limits, and nonworking dates are excluded.
A calculator can make timing arithmetic consistent, but it cannot infer missing policy language, operational constraints, or official exceptions. When the outcome affects employment, immigration, tax, contracts, health, or safety, confirm it with the governing source.
Practical use
Recommended workflow
Confirm relationship semantics in the project plan and test whether overlap is operationally possible.
Keep the final result as a planning artifact rather than an isolated number. Record who supplied each assumption, when it was checked, and what event should trigger recalculation.
Continue with the approval turnaround timeline when the next timing decision is known. The recurring compliance deadline generator provides a useful comparison when the assumptions change.
Input audit
Deadlines and projects planning checklist
- Locate the document or policy that creates the timing rule.
- Confirm whether dates are calendar days, business days, elapsed hours, or working hours.
- Record inclusivity, time zone, pauses, and exception rules.
- Set an internal action date earlier than the final modeled deadline.
Running this checklist before calculation prevents a precise answer from being built on the wrong calendar, rule, or source record.
Questions
Frequently asked questions
What is the difference between lead and lag?
Lag inserts waiting time; lead permits the successor to begin before the normal dependency boundary.
What should be checked before relying on the dependency lead/lag calculator result?
Business calendars, partial completion, multiple predecessors, resource limits, and nonworking dates are excluded. Confirm relationship semantics in the project plan and test whether overlap is operationally possible.
Which input has the greatest effect on the dependency lead/lag calculator?
The predecessor finish is calculated first. The selected finish-to-start, start-to-start, finish-to-finish, or start-to-finish relationship anchors the successor. The result models one dependency pair. Negative lag represents lead time and can create intentional overlap.