Why do we need an ex-dividend date? What is the problem with the ex-dividend date being the same as the payment date? Why are they separate? What problem does having a separate ex-dividend date solve?
For example, at the moment - a company announces a \$1 dividend on 12 May with ex-div date of 12 June and a payment date of 12 July. The stock price goes down by \$1 on the ex-dividend date of 12 June. The money goes out of the company to investors on 12 July. Between 12 June and 12 July, the stock is cheaper by $1 because it has been discounted (ex-div) but the money is still in the company's bank accounts.
What problem does this extra (ex-div) date solve? I can only see it introducing a risk or a mismatch because a company is entitled to cancel the dividend distribution past the ex-dividend date and not pay it out. I agree it is rare but it happens and is legal and possible. The only date where we are 100% sure that a dividend is in fact paid out or not (and the stock price should go down by \$1) is on the payment date when the money goes from of the company's account into the shareholders accounts.