why would you think that independent shields would cause other independent shields to change their spawn time?
they dont all lock into each other and form a mega shield or anything.
and no, they dont reset to some other shields time.
i have all shard shields and all of mine spawn on different dates.
i even have some on other shards locked down in other houses owned by other accounts of mine and they spawn on different dates.
if your talking ATL then maybe it has something to do with the crash ATL had yesterday?
maybe they reverted?