WordPress is set to UTC-17

For some reason, my WordPress install is having some strange timezone issues. Posts that are unscheduled (published immediately) aren’t published for 12 hours. For instance, I screencapped this. My computer clock shows 22:36. The WordPress clock shows 10:36, in 24 hour (military) time, as proven by the UTC timestamp of 15:36 directly to the left of the 10:36 timestamp.

I checked with my webhost, and as shown in this simple time.php file: it doesn’t seem to be the server time that is set incorrectly.

Deactivating all plugins did nothing to fix the problem. Switching to the default theme did nothing to fix the problem.

Is there any way to pinpoint exactly what would be causing the problem? Is there a known bug that causes this? Are there any particular database errors that could cause this?