What model sensor is this? The IDSM2, NM-CIDS, and SSM sensors doe not have a "clock set" command because they slave off of their host. If it is an IDSM2 then it gets its time from the switch (you would have to set time on the switch). Also, after making changes to the offsets (local and/or summertime) you will need to reboot the sensor to see the correct time.