Suppose I said the following:
I have always been happy until now.Do you think I am still happy?
In my variety of English, this would mean that things have changed, and now I am no longer happy; but my guess is that most people in Brunei and Singapore would feel that the state of happiness continues into the present time, so I am still happy.
This variant meaning of until now has the potential to create lots of misunderstandings. When we don't know a word, then there is not too much of a problem. But when we think we know what something means and it actually means something else, that is much more problematic.