Suggestion: Add master start date

[Ed Philpott]

I am working on a list for a future project with an unknown start date. I would like to have a master start date that all tasks would refer to. That way when I know the start date I would only need to change 1 field. Also, instead of storing the start date as an absolute date, store it as a value relative to the master start date. That way when the master start date is updated, all task and sub-task dates would be updated as well.
Thanks, Ed