[otrs] Timezone setting

Hi, We are in China (Timezone Beijing), while our server is located in USA. We found the time displayed in OTRS is always wrong, not our local time. And ticket from our client (also in China) and notification email always showing wrong time, but different from that in OTRS. We know timezone could be set in Config Options: Framework -> Core::Time, but we fail to find out the solution that really makes the time correct. Thanks a lot, Arlene