Timeline shapes - what do they mean?

[Sammi Girl]

When creating a flowchart, the shapes have meanings -- a standard.  Are there standard meanings for the different timeline shapes as well?

[Paul Herber]

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.

[Yacine]

If there are any definitions they would probably be mentioned somewhere deep in the project management norms.
http://en.wikipedia.org/wiki/Project_management

The germans would read
http://de.wikipedia.org/wiki/Projektmanagement

and refer to the DIN 69901