urgetn help date/time settings on debian

[Vijaya S <vijaya@picopeta.com>]

Hi all,
The mail server 's date and time has gone one day ahead and it has
debian unstable installed on it.
it shows Wed Aug 18 10:25:59 IST 2004
but the actual time and date now is Tue Aug 17 12:21:04 IST 2004
how do i get it right

Regards,
Vijaya