PDT stands for Pacific Daylight Time. It is a time zone used in parts of North America during Daylight Saving Time, usually from the second Sunday in March to the first Sunday in November. PDT is 7 hours behind Coordinated Universal Time (UTC−07:00). It is used in the western United States, parts of western Canada, and Baja California in Mexico. During the rest of the year, this region follows Pacific Standard Time (PST), which is UTC−08:00. In everyday usage, PDT is often referred to as Pacific Time (PT) or the Pacific Time Zone, but technically PT shifts between PDT and PST depending on the time of year. Major cities in the PDT zone include Los Angeles, Seattle, and San Francisco. PDT is 3 hours behind Eastern Daylight Time (EDT) and 1 hour behind Mountain Daylight Time (MDT) when DST is active. So, PDT is the daylight saving time variant of the Pacific Time Zone, observed in summer months to make better use of daylight.