What are common Java libraries for converting values into human-friendly strings?

Question

I'm looking for a library of utilities for converting "1234" into "1.2KB" or the date Tue 11:24pm into "2 hours ago". In particular, I'm expecting something vaguely similar to Django's notion of "template tags and filters" (see http://docs.djangoproject.com/en/dev/ref/templates/builtins/?from=olddocs).

Answer 1

for Date there I know one PrettyTime