In short
Engineering program management software divides into tools that plan (schedules, portfolios, stage gates) and tools that run the program as it is happening (holding commitments to the date and acting when one moves). The first kind is mature: Planisware, Planview, Microsoft Project, Smartsheet. The second kind is new, and it is what Tymeline is. A complex engineering program needs both, and the second is where the date is actually won or lost.
Planning software and its limit
A planning tool holds the intent: milestones, dependencies, owners, capacity. It is updated by people, so between updates it describes the past. On a program with fifty engineers and four suppliers the plan is wrong somewhere every day, and nobody knows where until a review.
Software that runs the program
Running software starts where planning software stops. It reads the engineering tools and the supplier traffic directly, so it knows the true state without being told. It holds each commitment to the date and works out the fix the hour one starts to move. It acts inside an authority envelope the company set, and writes a receipt. Its measure is simple: the committed date does not move.
What to ask a vendor
Ask where the truth comes from, and whether a person has to type it. Ask what happens in the hour after a supplier moves a date. Ask what the software is allowed to do on its own, and who set that boundary. Ask to see the record of one action, end to end. A planning tool answers the first question with a person's name. Tymeline answers all four with the program.