Data Type Yes/No (Yes/No field: A type of field with content set to either Yes or No; also known as a Boolean field or a True/False field. For example, the Recurring field indicates whether the task is a recurring task.)
Entry Type Calculated or entered (calculated or entered field: A field in which the value is determined by Project based on information in other fields. Information that you enter in the field yourself overrides calculated values.)
Description The Milestone field indicates whether a task is a milestone (milestone: A reference point marking a major event in a project and used to monitor the project's progress. Any task with zero duration is automatically displayed as a milestone; you can also mark any other task of any duration as a milestone.).
How Calculated If a task has a duration of zero, it is identified as a milestone and the Milestone field contains Yes. If a task has a duration greater than zero, this field contains No.
Best Uses Add the Milestone field to a task view when you want to change the automatic settings for milestones directly in that view. You can change whether a task is a milestone by changing the Yes and No designations in this field. You can also use the Milestone field to apply special formatting to milestone tasks in the Gantt Chart, the Calendar, or the Network Diagram views.
Example The final task in each phase of your project is a day-long review meeting with management. Because the task shows a one-day duration, Project does not automatically set it as a milestone task. You can change the Milestone field from No to Yes to make it a milestone anyway.
Remarks Another way to make a task a milestone is in the Task Information dialog box.
To apply text formatting, such as font style or color, only to milestones, in the Text Styles dialog box make sure you select Milestone Tasks as the item to change, then change the font, color, or size. The changes you specified are applied to all milestone tasks.