Timeline 1 - sequence of artifacts. Each artifact has a publication time.
Timeline 2 - sequence of changes to an artifact.
Timeline 1 - new pages are added, the system changes, contributors change.
Timeline 2 - changelog for an article.
Timeline 1 - git log.
Timeline 2 - if specific articles are going to undergo thorough changes, a changelog may be embedded.
Revision history up top.
http://catb.org/~esr/faqs/smart-questions.html