"David G. Johnston" <david.g.johnston@gmail.com> writes:
> The problem here is not timezone related - it is more fundamental in that
> the stored data does not change but the expression, as time progresses, is
> going to give different values and thus make what is stored incorrect.
Right --- current_timestamp in a generation expression makes no sense.
(There's also an issue about whether the surrounding calculation
is timezone-dependent, but that could be fixed up. Depending on
current time cannot be.)
You could create a view in which this value is an extra computed column,
but you can't do it as a stored generated column.
regards, tom lane