Date is a term that represents the specific period of calendar time upon which an event takes place, narrowed down to the day, month, and year, and in some cases narrowed to time as well. Along the life cycle of a project, every milestone will typically be assigned an estimated date of completion based on how long it is expected it will take to complete all preceding activities. However, these dates can always be changed if the situation merits. Examples of dates that are important to the management of a project are the estimated start date, the estimated date of completion, and the date of delivery of any specific products or items if that date should happen to differ from the date of completion. It is essential in setting a timeline at the outset that these dates all be considered carefully, however, in most cases they can be changed if the situation merits.
This term is defined in the 3rd edition of the PMBOK but not in the 4th.