For you, my speech is being delivered on the 11th of June, but my diary shows this important speech is scheduled for the 12th of June. We are communicating across the Pacific in real time, but the dates in our minds are different. As for the dates of a speech, I can rely on my secretary to ensure that there is no misunderstanding.
However, when it comes to finance, dates mean a lot more. Suppose I am committed to sending money to some of you two days from now. Should the money reach the recipient on the 13th, or on the 14th? Moreover, if both sides take account of mutual weekends, there are only 4 days in a week when transactions can be processed.