Mahara, the most open source E-portfolio, has now started following the date based version control system. According to the official forum post:
Our current numbering system does follow any numbering system strictly and thus, it does not offer too much insight into where Mahara is up to and how much change has occurred from one release to another.
We have decided to move to a date-based release versioning system for the Mahara releases. The format will be YY.MM.x where