Is it possible to build a project plan where the task dates are relative to completion project date.
For example, my project needs to be completed by 12/31/2026 and I need task one on that project to be assigned a month before project date (11/30/2026) , task 2 - 2 months before project completion date ( 10/31/2026) for example
Project Templates in Asana allow you to specify task and subtask relative due dates which either can be number of days prior to the project’s end date or number of days forward after the project’s start date. When you create each project from the template, you specify the project end date (in your case) and all the relative task dates are given their respective dates. If you didn’t want to use a project template, a third-party app, Flowsana.net (cc @Phil_Seeman) offers more direct support for what you’re asking for, I believe.
Optionally you can specify task dependencies which makes maintaining these relationships when dates move easier.
You can learn more about project templates and dependencies in help.asana.com.