USER TIME ZONE IN SU01

Dear All,

I have requirement to releated to User Time Zone. My X user want to posting date should be change according shift wise like (A, B, C). For Example : X user is woking in C Shift (11: 00 PM Date 19.04.2011 to 8 : 00 AM Date 20.04.2011) then posting date will be 20.04.2011 at 8:00 AM. At presently System change the posting date at 12:00. I want to posting date will be change at 8:00 AM on particular User.