thanks for mvandemar, posted in digipoint forum!Ok, due to the fact that very few people will actually read all of the posts in the current (and the past, and most likely the future) "PR Update" threads, I thought I'd post a nice little example of how to make sure something is actually happening.
When PageRank is updated (talking visual update here, anyone who thinks they're being intelligent by pointing out that behind the scenes PR is updated constantly should be slapped), Google bases it on a single snapshot from a specific point in time (same goes for BL updates, btw). That point in time is usually a few weeks prior to the actual export. When you are looking at PR, it is calculated by all using all of the links that Google knows about at that time. Any links you get to your site after than snapshot won't be counted, even if you get them prior to the actual PR itself being exported.
One of the spinoffs of this is that any webpages that didn't exist before the update will not have PR until the next update. This is important, especially with the current out-of-sync datacenter situation that Google has at this time. Currently there are certain datacenters that are still showing pre-August PageRank values for sites. What this means is that if someone looks at a webpage at different times, if the pre-August PR is different from the latest PR, sometimes they will see different results. Same thing when using a multi-dc PR checking tool... some DC's will have one value, while others will have the older, last year values.
People who do not realize this, and check their PR say, every couple of months using a multi-dc tool, might see what they think is a PR shift, and assume that the difference in values means a recent change. Hence, a new flurry of "PR Update" threads get spawned.
However, while this makes it slightly more difficult nowadays to check for PR updates, it does not make it impossible. You cannot reliably use pages that had existed going back 2 updates, but you can always use newly created pages, ones that did not exist prior to the last snapshot date. A good source of tracking down pages that we can pinpoint a date on and assume Google knew about the page back then, is popular blogs.
Look, for instance, at this page on Matt Cutts blog:
That page was created on 12/28/2006. We can safely assume that Google know about that page within a day or two (at most) of it being posted. Therefore, we know that the last snapshot date had to be after that post. Now, the very next post after that:
which is dated 12/29/06, is PR0. What's more, it is PR0 across all datacenters.
Works for other popular blogs as well, here's TechCrunch on 12/28 vs. TechCrunch on 12/29. Obviously the last PR snapshot date was around 12/29/06.
Therefore, before starting a PR Update thread, it is probably a good idea to base it around observations where you can actually show before and after data, rather than just "I see changes" types of responses.