International Date Line
For two hours every day, at UTC 10:00–11:59, there are actually three different days observed at the same time. At UTC time Thursday 10:15, for example, it is Wednesday 23:15 in Samoa, which is eleven hours behind UTC, and it is Friday 00:15 in Kiritimati (separated from Samoa by the IDL), which is fourteen hours ahead of UTC. For the first hour (UTC 10:00–10:59), this phenomenon affects inhabited territories, whereas during the second hour (UTC 11:00–11:59) it only affects an uninhabited maritime time zone twelve hours behind UTC.