DateTime set: Object cannot be written

Very lately (about fifteen minutes ago) I had to resolve the time issue from the ELOM level of Sun Fire X2200.
It couldn't be done, because:

/SP/AgentInfo -> show 

  /SP/AgentInfo
    Targets:
        PEF
        PET
        SEL
        console
        mail
        SNMP

    Properties:
[...]
        DateTime = 01/03/1970-02:56:23
[...]

/SP/AgentInfo -> set DateTime="09/22/2009-00:22:00"
set: Object cannot be written

So, it's the place where the ipmitool could be used.
Ipmitool need the three kernel modules to be loaded:
* ipmi_si
* ipmi_devintf
* ipmi_msghandler

The time can be adjusted with an argument set of the ipmitool's SEL (System Event Log) subcommand.
Sample Linux command line session:

# ipmitool sel time get
Could not open device at /dev/ipmi0 or /dev/ipmi/0: No such file or directory
Get SEL Time command failed
# lsmod | grep ipmi
# modprobe ipmi_devintf 
# modprobe ipmi_si      
# lsmod | grep ipmi
ipmi_si                57164  0 
ipmi_devintf           20624  0 
ipmi_msghandler        50680  2 ipmi_si,ipmi_devintf
# ipmitool sel time get
01/01/1970 22:07:22

# ipmitool sel time set "09/22/2009 00:22:00"

# ipmitool sel time get
09/22/2009 00:22:03