July 13, 2014
October 27, 2013
August 1, 2015
Money only moves on business days externally, and even then only a few times a day. It's batched (both bill payments and EFT). Institutions write an instruction about moving money from somewhere to somewhere else. It gets transferred. The other institution reads in the instructions and then reflects them on their side. This happens a few times a day and when it is all done depends on when your instruction is written in.
A financial institution may allow you to "pay" a bill on a weekend but nothing will actually happen until the next business day externally.
Payments Canada is looking to improve it to be faster but I don't believe that includes weekends, just faster (and eventually realtime) during business days.