Incorrect date/time returned by CURRENT_TIMESTAMP

Hi,

My implementation of Postgresql is as followes:

Postgresql Version: PostgreSQL 7.2.1 on i686-pc-cygwin, compiled by GCC
2.95.3-5
Cygwin dll: 1.3.10
Operating system: Windows 2000 Service Pack 2
Processor: Intel Pentium III 1 Ghz
Bios: Award Moduler Bios v6.00pg

When I start postmaster and run 'select CURRENT_TIMESTAMP;', the date
and time
are correct. After a hour, I run 'select CURRENT_TIMESTAMP;' and see
that the
time is not the same as the system clock, in fact it is quite far
behind.

Can someone please tell me what could possibly be causing this.

Thanks
Colin