PDT, or Pacific Daylight Time, is a time zone that is 7 hours behind Coordinated Universal Time (UTC-7). It is observed during the summer months when clocks are set forward one hour from Pacific Standard Time (PST), which is UTC-8. PDT typically begins on the second Sunday in March and ends on the first Sunday in November. This time zone is used in several regions, including parts of California, Washington, and Oregon. The shift to PDT allows for longer daylight hours in the evening, which can benefit outdoor activities and energy conservation.