A job application in England wants applications to arrive by the 30th. I understand this to mean by the end of the 30th (in London time). The accepted answer to this question appears to indicate the same. However, it is now clear that the English who posted this meant by the beginning of the 30th, meaning the end of the 29th. This surprised not only myself, but also a Canadian colleague. This happened at two independent instances.
Is there a difference between American/Canadian English and British English in what is colloquially meant with by the 30th, by Friday, etc.?
(The related question Does "notified by [date]" include the end date? does not address whether there is an American/British English difference)