Funny things bank transfers. Payments are made through SWIFT
. From the Wikipedia article:
SWIFT does not facilitate funds transfer: rather, it sends payment orders, which must be settled by correspondent accounts that the institutions have with each other. Each financial institution, to exchange banking transactions, must have a banking relationship by either being a bank or affiliating itself with one (or more) so as to enjoy those particular business features.
As far as I can tell, and I could be wrong, in Greece the major banks, i.e. Alpha Bank, Eurobank, National Bank of Greece and Piraeus Bank have a direct relationship with SWIFT while the smaller banks, such as the various cooperative banks, do not seem to have a direct relationship with SWIFT. They rely on receiving payments by being affiliated to one of the major banks. That seems to make payments a bit slower to these smaller banks and occasionally transfers fail and the money gets returned.
In my experience payments to the major banks are very fast, e.g. showing on the statement the following day but with a recorded date of payment the same as the date of transfer. That is because, even if it arrives the same day, transactions are processed overnight so don't appear on the statement until the following day. Sometimes it might show an availability date, i.e. funds have cleared, a couple of days after the recorded date.