Currently there each tasks can only have two dates associated: a "start" date and a "due" date.

It would be nice to have three dates per a task:
- a "start" date,
- a "scheduled" date (or a "do date"), and
- a "deadline" date.

Currently I use the due date in the app as a scheduled date, and each day I clear out my daily list (à la the Systemist method https://todoist.com/productivity-methods/systemist ), which often involves postponing tasks to other days. But this means that I can accidentally postpone a task until after it's hard deadline. If there was a separate "deadline" date then a warning could pop up just as it does now when the start date is later than the deadline.

I can't use the start date as a stand-in for my scheduled date because I already use the start date to keep track of tasks that I'm actually unable to do anything about until that date passes.

I believe this idea might be getting at the same thing, but I've not used Astrid: https://www.rememberthemilk.com/forums/ideas/10053/

This is also related: https://www.rememberthemilk.com/forums/ideas/12304/