I have a similar problem, the Server OS has the correct date/time, also the client OS, even the BIOS in both cases.
When I open Calendar, it is always one day forward.
I have test with differet timezone combinations, but the problem persist.
I haven't found anything similar on the Forums or Bugzilla but this Thread.
OS: SLES10 (i586)
Release: 5.0.11 SuSEES10 NETWORK
Timezone: Caracas (Venezuela)
Browser: Mozilla Firefox 3.0.3