PDT or Pacific Daylight Time is the time zone used in the western part of North America during the summer months. Some common synonyms for PDT include Pacific Summer Time, Pacific Daylight Saving Time, and PT. PT is commonly used in the winter months when the Daylight Saving Time is not in effect. Other related words that may be used in conjunction with PDT include time zones such as Mountain Daylight Time, Central Daylight Time, and Eastern Daylight Time. These time zones are used throughout North America in order to coordinate activities and stay on schedule. Knowing the correct time zone is important for scheduling appointments, flights, and other activities.