Here's summary of the last 2 updates:
ON Feb 23, 2012 : Now processing March 8, 2011
ON Feb 29, 2012 : Now processing March 22, 2011
ON Mar 7, 2012 : Now processing April 11, 2011
Looks like the formula used by Processing Period Chart is this:
An average of 17 days of jump for every 1 week
If my Math is correct, applying geometric series estimation, this means cutting the processing time for Stage 1 every month. So that means, by April 2012, they will be processing June 2011 applications. Then by June 2012, they will be processing Oct 2011. Then by July 2012, they will be processing Dec 2011 applications.