Complex sentence: The UTC − 04 Standard Time Zone is used in northwestern Greenland, and the area around Thule Air Base observes North American DST rules, known in Canada as the Atlantic Time Zone and in the Caribbean as the "Eastern Caribbean Time Zone".
Split into simpler sentences: The UTC − 04 Standard Time Zone is used in northwestern Greenland. However, the area around Thule Air Base observes North American DST rules, known in Canada as the Atlantic Time Zone and in the Caribbean as the "Eastern Caribbean Time Zone".