WLS 10.3.6 : Log rotation not accepting simpleDate format : "server.log.yyyy_MM_dd-hh"

 Hi,

I am trying to get this log file to rotate hourly, but for some reason it is not taking the date format. 

Instead, it creates a log file which is literally named "server.log.yyyy_MM_dd-hh". 

I have tried multiple variations of the variable placement, but nothing seems to work.

The log file name that I would like to end up with would be server.log.20121211-09   ( ie: server.log.yyyymmdd-hh)

I have tried this both in WLST, and via the admin GUI.

instance = "t3://hostname:7001"

connect('*****','*****',instance)

edit()

startEdit()

cd('/Servers/serverName/Log/mob02')