In the Modify Global Change dialog box, you can add or subtract a date from one another to calculate the number of workperiods between them, based on the activity or resource calendar. The following example find the difference between a baseline and the open project's start dates, based on the activity calendar:
30-Jul-02 - 27-Jul-02 = 3
Start - BL Start = (User_number field)
You can add a number to a date to calculate a new (later) date, or subtract a number from a date to calculate a new
(earlier) date. For example,
27-Sep-02 + 3 = 30-Sep-02
27-Sep-02 - 3 = 30-Sep-02