How are the phase dates calculated?

Each phase starts the day the previous one ends, so they chain back to back from your chosen start date. Phase length varies around the average you set, giving realistic but reproducible spans.

What drives each phase status?

Status is computed against today's date. Phases that have already ended are completed, the phase containing today is in progress with a percentage, and phases starting later are not started yet.

How is the progress percentage derived?

For the in-progress phase, progress is the fraction of elapsed time between its start and end dates, clamped between 1 and 99 percent. Finished phases show 100 and future phases show 0.

Why do milestone dates fall inside a phase?

Each milestone is assigned a random day offset within its phase, then the milestones are sorted by date, so they always land between the phase start and end in chronological order.

Is the output ready for a Gantt library?

Yes. Each phase carries an id, name, ISO start and end dates, status, progress, and milestones, which maps cleanly onto most Gantt and project management data models.

Project Timeline Generator

A project timeline data generator that produces sequential phases, milestones, and dates as clean JSON. It is built for testing Gantt chart renderers, project management tools, and PM app demos with realistic but disposable data.

How it works

You set a start date, a phase count, and an average phase length. The generator chains phases back to back: each one begins the day the previous ends, with its duration varied around your average so the schedule looks organic. Within each phase it places two to three milestones at random day offsets, then sorts them chronologically so they always sit between the phase’s start and end.

Status is computed live against today’s date. A phase that has already finished is marked completed at 100%, the phase containing today is in progress with a percentage based on elapsed time, and later phases are not started at 0%. Everything is seeded, so identical inputs reproduce identical output; Regenerate advances the seed.

Tips and example

For a typical software project, try five phases at a 14-day average from today. You will get phases like Discovery, Planning, Design, Development, and QA, each with dates and milestones. A phase object looks like this:

{
  "id": "P2",
  "name": "Requirements & Planning",
  "start": "2026-06-20",
  "end": "2026-07-03",
  "status": "in_progress",
  "progress": 42,
  "milestones": [
    { "name": "Spec finalised", "date": "2026-06-28" }
  ]
}

Toggle to the readable list to eyeball the schedule, then copy the JSON straight into your test fixtures or seed data.