Yesterday (April 16), the PR of the Blog Union dropped from 4 to 2, which doesn't seem like a fluctuation because all server queries for PR data returned a value of 2. However, upon checking other websites, no changes were observed, including the homepage and inner pages of this blog, which remained unchanged. If this was truly a PR update, why didn't other sites change? According to the PR update pattern, the predicted time for this update should fall within May.
I checked the PR update schedule on Webmaster Home and http://www.seocompany.ca/pagerank/page-rank-update-list.html (the data from this link should represent the PR update times for foreign sites), and the data still shows the update times for January and February of 08. Screenshots from both sites indicate that PR updates seem to have lost their regular timing pattern.