Date: Can it be specific to a shell??

[anthony zador]

 How does the UNIX date command know the date?
Is there some file that is updated?
Must date be the same to all shells on a given machine, 
or can su selectively adjust the date for a given shell?
If a machine A is the disk server for B, what determines
the date-stamp for a file, A or B?

If someone could answer these questions, or even point
me to one step beyond the man page on date
I'd appreciate it.

Thanks, 
Tony  Zador