3 years ago my highest traffic day(from natural search) was Saturday. Since then it has very gradually shifted thru Sunday and then Monday and it now rests firmly on Tuesday. My weekly stats result in graphs that look like a saw blade with the peaks consistently on Tuesday.
Additionally it's not that my total traffic has increased more quickly on Tuesday, it looks like the traffic from other days has both changed in quality and has receded slightly despite overall growth in total.
Is it because the site has a handful of affiliate offers and it sells no product that perhaps search engines direct people to other sites on peak shopping periods? My transactional traffic(traffic to pages with an affiliate link) is down and informational traffic(pages with no offers) is conversely up... but why Tuesday?