It seems the new notification panel code doesn't take timezone preferences into account correctly, or uses UTC where it shouldn't.
- Generate a notification (e.g. thank yourself from another account)
- Set your timezone preference to America/Los Angeles
- Note that the notification is reported as "8 hours ago" even though it just happened
- Change your timezone preference to Europe/Amsterdam
- Note that the notification is now reported as being in the future: "in one hour"