Open Houses- Better showings on Saturday or Sunday?

Lately I've seen an increasing number of open houses on Saturday afternoon.  I co-hosted an open house on a Saturday and was delighted that 17 groups of people showed up with only advertising on Realtor.com and signs in the neighborhood.  We held another open house the next day and only 7 groups of people showing up.  Acknowledging cannibalization from Saturday, do you think Saturdays are another way of capturing potential clients?  I want to comment also that several groups of people showed up between 4-6pm, which I found slightly surprising and encouraging.