FS timestamp issue running Debian in Vbox

[Mark Allums <mark@allums.com>]

Running Debian on Virtualbox (under Win 7, alas), taking a VBox snapshot 
screws up the filesystem mildly, somehow affecting timestamping.  Of the 
virtual hard disk in such a way as to confuse the booting kernel.  No 
corruption takes place, except to alarm the init scripts or the kernel 
fs bits into thinking there is an inconsistency.

An fsck always fixes it.  The error message is something like:

Superblock last write time (>date<,
        now = >some other date<) is in the future.
Fix<y>?

I always answer yes, and everything is fine.

I assume there is a discrepancy between the *nix assumption of system 
clock set to UTC, and Win assumption of clock set to local time, but 
what is there to be done to fix it?

In particular, why does making a snapshot affect a superblock?  This 
can't be good.

Any suggestions? I hate running fsck every other reboot.

Mark Allums