Well, that's the problem with badly written code. It's tough for maintainers. You'll have to examine the whole code base and see how they are using those patterns. They are probably using the patterns to instantiate SimpleDateFormat instances. If you're lucky, they're setting these all up in the same place. You can change those to DateFormat.getXxxInstance() calls, like DateFormat.getDateInstance(SHORT, myLocale).
On the other hand, you could just make literal Strings matching what you found in Java 1.5, and shove them in your patternTable. That kicks the rewriting job down the road a bit, but still leaves you with badly written code.