Online banking not 24/7, what gives

You would think in the internet age, that online banking would be available 24/7. Why be constrained by normal banking hours, normally Mon - Fri, 9 - 5? Tonight I try paying my Visa bill, and scheduled it for Sat 7/16, 1 day before it's due date of Sun 7/17. After I submitted the form, the date got changed to 7/18. The 16th is a Saturday, so apparently the logic changes the date to the next normal business day, which in this case is the 18th, Monday. Well, if I didn't pay close attention, I would have been nailed with a finance charge, just for that small 1 day late payment. So I cancelled the payment, and changed it to Friday, 7/15. Come on, why can't internet banking be just like all other online businesses, open ALL the time?