Abstract: A method and system for modifying a project model in response to an update. The project model including a plurality of activities, wherein each activities includes an early start date and a late finish date. A number of activities are initially added from the project model to a list in response to an update. Each activity added to the list is directly affected by the update. For early dates, an activity with an early start date that precedes all other early start dates with respect to other activities within the list is removed. Then, the early start date for the removed activity is redetermined in response to the update. Activities which succeed the removed activity and which are related to the activity to the list are added to the list if absence of a match between the redetermined early start date and the early start date associated with the removed activity exists.