Hi everyone 
Great news: Subtask Date Rollups are now live in Asana! 
Thank you to everyone who requested this and shared your feedback here. It really helped shape the feature.
With a rollup, a parent task’s start date moves to the earliest subtask start date and its due date to the latest subtask due date. You can roll up a single parent task or a whole project at once, and nested subtasks are included too.
Just a heads-up that rollups are manual (run them again if subtask dates change) and they only update dates already set on the parent. Project-wide rollups can’t be undone, so double-check before confirming.
Give it a try and let us know what you think! 