You have my sympathies. I eventually fled my Big Bank and left for saner pastures (aka credit union/online bank).
The unfortunate part is that this doesn't have to be a mystery. Back in the day, when I deposited a check, World Savings would give me a small slip of paper that said (approximately):
Available Now: $50In 10 Days: $X + $50In 20 Days: $Y + $X +$50(and so on)