Project Timezone Always Reverts to Etc/GMT+12 (UTC-12), and Deadline Changes

No matter how many times I change a project's time zone to the correct one and save it, it always reverts to Etc/GMT+12 (UTC-12).

And it also sometimes ends up changing the actual Project Deadline by one day. For example it swaps my deadline to July 30th from July 31st no matter how many times I save it.