In Belgium, we say 25 as "five and twenty" (same as German), which makes sense, but if you've been saying "twenty-five" for 10 years, it does throw you off.
"five past five" is 5:05, then of course "ten past five" and "quarter part five". Then comes "ten to half six" which would be 5:20. Then half six, ten past half six, quarter to six, ten to six and five to six.
It's interesting to see how Dutch and German time telling is clearly oriented at half hours while English is oriented at whole hours.
Now that the world is ruled by digital clocks, many people will just use digital (24 hour) time. "Eighteen hour four" would be the current time in this notation, which is a lot simpler. It's funny how the tool we use to tell time dictates the way we pronounce things!
(I bet something like 20% of people would think hard and then decide you meant 2:30)