Duration of a project

Project

A project in business and science is typically defined as a collaborative enterprise, frequently involving research or design, that is carefully planned to achieve a particular aim. Projects can be further defined as temporary rather than permanent social systems that are constituted by teams...

's terminal element is the number of calendar periods it takes from the time the execution of element starts to the moment it is completed.

Do not confuse duration with work

Work (project management)

Work or Work Package in project management is the amount of effort applied to produce a deliverable or to accomplish a task or a group of related tasks defined at the same level in the WBS....

. E.g. it takes three days for a snail-mail letter to arrive from point A to point B, whereas the work put into mailing it may be 0.5 hours.

Strictly speaking, the phrase Duration of terminal element X is 5 days is incomplete. It fails to specify the following:

• the probability
  Probability
  Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we arenot certain. The proposition of interest is usually of the form "Will a specific event occur?" The attitude of mind is of the form "How certain are we that the event will occur?" The...
  
   with which the completion is expected in the time allotted (since any estimate is only a prediction about the uncertain future, see critical chain
  Critical chain
  Critical chain project management is a method of planning and managing projects that puts the main emphasis on the resources required to execute project tasks. It was developed by Eliyahu M. Goldratt. This is in contrast to the more traditional critical path and PERT methods, which emphasize task...
  
  )
• the resources
  Resource (project management)
  In project management terminology, resources are required to carry out the project tasks. They can be people, equipment, facilities, funding, or anything else capable of definition required for the completion of a project activity. The lack of a resource will therefore be a constraint on the...
  
   to be used (sometimes using more resources or different resources speeds things up)
• the assumptions which were made
• the author of the estimation
• the date the estimate was made
• the work schedule of the resources
• etc.

So the improved statement could read:

I, Marek Kowalczyk, as of 27 March 2005 strongly believe that if I fully applied myself to competing terminal element X and worked 8 hours a day every day, including holidays, and had all the materials at hand, then I would have completed it in 5 calendar days. See metamodel.

It may seem unwieldy to use such complicated statements, but lack of detail often leads to misunderstanding.