When creating flowchart, each shape has a purpose or a meaning. What about
timelines? What do each shape mean? Are there standards? Any "official"
answers?
Do you mean the different types of timeline and milestone? I don't think they have any
meaning, just use whichever looks best to you.
You could use the milestone shapes, for things like:
milestones that have passed early (yeah, I know, don't bother with this one)
milestones that have passed on time
milestones that have passed late
milestones *you* need to meet
milestones the project needs to meet
milestones that the customer wants (but ain't gonna happen! ;-)
You can change the milestone type from the right-click menu.