The duration of an activity is a derived value based on the method of construction selected for the work and the available material, labor, and equipment need to complete the work. In most construction schedules duration is expressed in working days. If there are differences in the working times and work-weeks of crews on your site, then care must be taken to ensure that the coordination of work between these crews can be accomplished.

The measurement of the original duration versus the remaining duration of an activity is of critical concern when updating a progress schedule. Separating remaining duration from earned value is an essential technique for effective project managers.