This article explains how the plan level fields Estimated Start and Estimated End fields function.
The Estimated Start and Estimated End fields are located in the Plan Details of a given plan, and are directly related to the Start and Due date fields in the plan's Work Plan.
Estimated Start = the earliest Start date in the schedule, or the Plan Start Date.
You can set a date in the Estimated Start field in the Plan Details form, which will set both the first Start date field in the work plan, and Plan Start Date.
Or, you can set the Plan Start Date, which will drive the Start field in the Work Plan, and Estimated Start field in the Plan Details.
