An interesting WebmasterWorld thread has a theory that for some sites, Google may give that site higher ranking based on what day of the week it is.
The SEO has been tracking the traffic from Google to the site for months. He noticed that every Tuesday showed the highest level of referrals from Google, but every Saturday showed the least traffic from Google. Over the past five weeks, he also has been tracking how many pages Google shows were indexed from the site using the site command (which he and we all know is not 100% accurate). The pattern remained the same, more pages were indexed on Tuesdays, the days he saw the most traffic from Google. Whereas, on Saturdays, less pages were indexed and less traffic was seen from Google.
WebmasterWorld, administrator, tedster, said "ranking changes based on day of the week definitely occur - they even get mentioned in some of Google's patents."
After a few more days, the thread creator noted that everything changed this week, after months of tracking. He said:
Final update, just when I thought I had sufficient data to start tracking related considerations for effect Google changed gears on me, Today's traffic should have been trending downwards until Friday (though up from last Wednesday) but instead the site enjoyed a record up day... breaking a long running trend.
I suppose nothing ever stays still long enough to fully evaluate online, ah well.
Coincidence or truth to this phenomenon?
Forum discussion at WebmasterWorld.