Mountain Standard (no DST) (MST)
Phoenix operates on Mountain Standard (no DST) (MST). Arizona (except the Navajo Nation) does not observe Daylight Saving Time, so Phoenix stays on Mountain Standard Time year-round.
Time Zone: Mountain Standard Time (MST) — Standard Offset: UTC-7 (MST) — DST: Not observed
Country: United States
This city does not observe Daylight Saving Time. The UTC offset remains constant year-round, which simplifies international scheduling.
Arizona is one of only two US states that don't observe Daylight Saving Time (the other being Hawaii). Phoenix stays on MST (UTC-7) year-round. This creates a unique scheduling situation: during winter, Phoenix is in the same time as Denver and Salt Lake City (MST). But during summer, when those cities shift to MDT (UTC-6), Phoenix effectively aligns with Los Angeles and San Francisco (PDT, also UTC-7). You essentially need to recalculate Phoenix's relationship to other cities twice a year — but Phoenix itself never changes.
Arizona opted out of DST in 1968, largely because the extra hour of evening sunlight in the desert was seen as undesirable — summer temperatures routinely exceed 110°F (43°C), and residents preferred the sun to set earlier. The exception is the Navajo Nation in northeastern Arizona, which does observe DST to maintain consistency across its territory that spans into Utah and New Mexico.
Phoenix has become a major technology and semiconductor hub. Taiwan Semiconductor Manufacturing Company (TSMC) is building a massive $40 billion fabrication facility in the Phoenix suburbs. Intel's Chandler campus is one of its largest manufacturing sites globally. The permanent MST offset simplifies coordination with Asian semiconductor partners — the offset to Taipei never changes, which is a genuine operational advantage for supply chain management.
The key to scheduling with Phoenix: always check the season. In winter, Phoenix is 2 hours behind New York and 1 behind Chicago (same as other Mountain cities). In summer, Phoenix is 3 hours behind New York and 2 behind Chicago (because they've sprung forward and Phoenix hasn't). The simplest rule: from November to March, treat Phoenix like Denver. From March to November, treat Phoenix like Los Angeles.