When looking at the commitment graph for old proposals, the year is missing. For example, Unix & Linux has a commitment graph labelled only "Jul 16 Jul 24 Aug 1 Aug 8". There is no indication of the year.
You can display the year a proposal went through Definition or Commitment by hovering over the date it started (hovering over '4 years ago' shows "2010-07-13 04:04:27Z").
But adding the year to the graph isn't something anyone is likely to address. The graphs were designed to be a visual way to show a proposal's progress. Years after the fact, the site has been created and the whole issue is somewhat moot.