Time zones
What do PDT, MDT, CDT and EDT mean?
The four daylight-time abbreviations used across the contiguous United States, their UTC offsets and their standard-time partners.
The “D” means daylight time
PDT, MDT, CDT and EDT are the daylight-saving versions of the Pacific, Mountain, Central and Eastern zones. During daylight saving time, clocks are one hour ahead of their standard-time setting: PDT is UTC−7, MDT is UTC−6, CDT is UTC−5 and EDT is UTC−4.
What they become in winter
When daylight saving time ends, the abbreviations normally change to PST (UTC−8), MST (UTC−7), CST (UTC−6) and EST (UTC−5). The broad region name—PT, MT, CT or ET—is often safer when you do not want to state whether daylight or standard time applies.
The exceptions matter
Most of Arizona remains on MST throughout the year, while Hawaii uses HST and does not change its clocks. US territories also have their own rules. For dates in 2026, most participating US locations observe daylight saving time from March 8 at 02:00 local time until November 1 at 02:00 local time.