allow relative dates in Gantt (eg m1,m2,m3)

[VladimirAlexiev]

Is your feature request related to a problem? Please describe.
While a PM is making a plan, very often the project start date is not yet known.

• This is especially true when writing a research proposal or responding to an RFP: the PM has no control over when (or indeed whether) the project would start.
• It's more informative/polite to show relative dates to the recipient, rather than tying to a "randomly picked" start date
• In particular for Horizon Europe research proposals, the schedule is shown in months since project start

Describe alternatives you've considered

• MS Project and most other project planning software has a separate attribute "project start" and the first task(s) don't (need to) have an explicit start date, but use the project start

Describe the solution you'd like

• (optional) Allow the specification of relative input dates in dateFormat
  • Eg m1, m2, m3 for "months since project start"
  • One could pick an "easy to work with" start date (eg 2023-01) and calculate from it.
  • But it's harder than working with relative dates. Eg if a task should be "from m10 to m14", I need to calculate in my head that's "from 2023-10 to 2024-02"
• (mandatory) Allow the specification of relative output dates in axisFormat

[sebnyberg]

This is also valid in other contexts, such as working with queue theory and schedulers. You're concerned with the number of tasks and their duration, not the precise time when the first task starts being processed (it's just t=0).