I use Jboss Seam 1.2.0.PATCH1
This probably has nothing to do with it, but out of interest which version of Java are you using?
I use "Java HotSpot(TM) 64-Bit Server VM (build 1.6.0-b105, mixed mode)" and Jboss 4.0.5.
It's a known issue with dateConverter. By default GMT is used. If your server isn't in GMT+1, then... the first day of a month can become the last day of the previous month!
To avoid this:
- fixe timezone explicitly
- use joda library
- use a converter as the one you tested
If your server is in GMT+1
Sorry for the noise.