I have been in situations where payday has been monthly, semi-monthly, bi-weekly and weekly. Just depends on the employer.
yes, you are right BUT - it's very, I mean very uncommon in Poland... i don't know a single person who work fulltime and get salary every week, every other week or sth... everybody have monthly pay day. Moreover it's very uncommon to ask your future employer (say during interview) when is the pay day... it's just because everybody by default think that he will receive salary on some specific day every month.