My database has some last_modified entries
just containing the year (2004, as it is)
or "0", leading to wrong "last modified"
dates in January, 1970 (2004) or displaying
the current date and time for "last modified".
A simple check can catch those wrong entries,
as there can't be any valid modification dates
before 1990 (not even after an import from
some older blog software).
Signed-off-by: Thomas Hochstein <thh@inter.net>