are the building blocks of a schedule. They have a start date and a finish date, represented by end nodes, and they span a certain period of time. In addition to a regular activity, there is also a delay/gain object, which is unique in that it can have a duration of zero. If the duration is zero, both the start and end nodes align to the start of the day (or whichever time unit has been selected). Delays are useful for showing positive or negative impacts to the schedule or for atypical activities. Unlike regular activities, delays cannot have an embedded node or any resources assigned. Delays can be distinguished from regular activities by their bar, which includes vertical gaps from the top to the bottom.
This chapter includes details for the following: