How does rolling back domain time affect database applications

Hi All
One of our hosted clients is not syncing from an external time source and as such is approx 20 mins ahead. Not a problem for us but our backup and tape change teams are logging times and want everything neat and tidy.
I was thinking of rolling back time on the pdc emulator (maybe 3 mins at a time).

My question is, how will this affect any SQL/exchange/oracle apps that are using time for logging etc.

Is there a best practice for dealing with this?

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A.Rajesh Khanna