The spot rate is simply the current interbank (or wholesale) market rate as determined by supply and demand, and is what is reported on sites like this one.
Apart from a retail transaction (over the counter), in a wholesale spot transaction the currency that is bought will be receivable in two days while the currency that is sold will be payable in two days. (This applies to all major currencies with the exception of the Canadian Dollar, which is dealt “same day”.)
In retail transactions you pay and receive currency on the same day, apart from T/T transactions which will usually take two days to appear in the receiving account.
You can contact XE here.