Which, as observed, is when the series was being written: from 1987 to early 1996. Obviously, Takahashi couldn't predict the future to know what technology would be available or what it would look like years after she'd moved on from writing the series. But computers and a calendar aren't plot -- they're extremely minor background details. Nothing in the actual story of Ranma prevents it from being moved forward in time. Nor that I can think of anyway. This probably seems like semantics, but I don't think it is.
Even if you disagree, it's still a nice pic, well-drawn and nicely colored.