EST to MST Converter

At 9:00 AM in New York, Denver clocks read 7:00 AM. That two-hour gap between Eastern and Mountain time holds steady across both standard and daylight periods, until you add Phoenix to the equation. Most of Arizona stays on Mountain Standard Time (UTC-7) all year. When the rest of the Mountain zone springs forward to Mountain Daylight Time (UTC-6), Phoenix stays put. Suddenly a city that shares Denver's winter clock sits three hours behind New York, matching the Pacific coast without ever leaving Mountain time.

The Fixed Two-Hour Gap

Eastern Standard Time runs at UTC-5. Mountain Standard Time runs at UTC-7. Subtract one from the other and you get two hours, every time. A 9:00 AM call from Washington D.C. reaches Denver at 7:00 AM. A 5:00 PM East Coast deadline hits Colorado at 3:00 PM. The arithmetic does not drift.

The labels change with the seasons. From the second Sunday in March through the first Sunday in November, Eastern shifts to EDT (UTC-4) and Mountain shifts to MDT (UTC-6). The gap remains two hours. In July, noon in New York is 10:00 AM in Denver. Same separation, different acronyms.

When Both Zones Change Together

The switch happens on a single schedule nationwide. At 2:00 AM Eastern on the second Sunday in March, clocks jump forward. It is 1:00 AM Central, midnight Mountain, and 11:00 PM Pacific the night before. Every observing zone moves in lockstep.

The return to standard time arrives the first Sunday in November. At 2:00 AM local, clocks fall back one hour. Both Eastern and Mountain zones participate, except for the one part of Mountain country that refuses.

The Arizona Exception

Most of Arizona ignores daylight saving time entirely. The state stays on Mountain Standard Time (UTC-7) through the summer. The result is a seasonal split:

• November to March: Phoenix and Denver both sit on MST. Two hours behind New York. No difference between them.
• March to November: Denver moves to MDT (UTC-6). Phoenix remains on MST (UTC-7). Phoenix is now three hours behind New York and one hour behind Denver. Its offset matches Pacific Daylight Time, though it is not PDT.

The Navajo Nation, which spans Arizona, New Mexico, and Utah, observes DST. Inside the Navajo Nation, the Hopi Reservation does not. On a summer drive through this territory, the clock can change twice without leaving the county.

Why Arizona Stays Put

Arizona exempted itself from DST in 1968 under the Uniform Time Act. The reasoning was local and practical: an extra hour of evening sunlight in summer means an extra hour of triple-digit heat. Air conditioning costs rise. The state decided the trade-off was not worth it.

Hawaii made the same choice for a different reason. At that latitude, day length barely fluctuates across the year. Shifting the clock saves nothing.

Conversion Table: Eastern to Mountain

The table assumes both locations observe the same type of time. For Arizona in summer, add one hour to the Mountain column.

Quick Reference: New York, Denver, Phoenix