500+ Views on Photostream Sunday - Why?

Photos on my Flickr Photostream received an all-time-one-day high of 502 views yesterday, April 12...and I can't figure out why.

I think I've taken some great pictures over the years and that I've grouped the 557 I've uploaded so far into sets that make sense. But, most days I get somewhere between 20 and 40 views. Occasionally there will be a spike in views up to 100 or so, only to return back to the normal 20, 30, 40 range within a day.

Yesterday, however the view totals shot way, way up. By using the Flickr stats tool, it appears that people were looking at all kinds of pictures - so no discernible patterns. Pictures I took in China seemed to have a few more views than others, but again, pictures of all different subjects and locations were viewed.

It also looks like most people came to my Photostream through searches on Flickr itself, with a few more coming in via Yahoo! and Google.

Anybody have any theories? Could it be that randomly an abnormally high number of people found my photos on Sunday? Or, could there be a reason? Someone or some group specifically looking at my pictures? Or, looking at subjects that I have well represented?

I welcome any guesses or insights from people who know the ways of search engine or Flickr.