>I'm developing a global web site, have questions about the datetime fields [sic]. How to handle it if user comes from difference time zone? Any guidelines for this? <<
Yes, there are. Read the ANSI Standards. If this is a serious
problem for you, then consider using DB2 which implements the
Standards. If you are stuck with SQL Server, then you will have to do
it all by hand yourself while waiting for the 2008 version to give you
some more help.
The basic idea is that all times are kept in UTC and you have a table
for the time zones and DST displacements. This means you need VIEWs
and INSTEAD OF triggers to hide the computations from the
developers.