I'm using RollingFile appender with archiving to a separate directory.
The archive directory pattern is yyyy-MM.
Up until 2013-08-30, everything worked just fine.
All the logs for August were placed inside directory 2013-08
On 2013-09-01 00:01, log4j2 placed the log for 2013-08-31 inside directory 2013-09, instead of 2013-08
-bash-4.1$ ls -l 2013-09
rw-rw-r- 1 tomcat tomcat 4846 Sep 1 00:01 rws-2013-08-31.log.gz
Here's the configuration I'm using: