MST to EST

"MST" is used for two different behaviors. Colorado, Utah, New Mexico, Wyoming, Montana and southern Idaho switch to Mountain Daylight Time (UTC−6) from the second Sunday of March to the first Sunday of November, keeping a steady two-hour gap to New York. Most of Arizona stays on Mountain Standard Time (UTC−7) all year, so from March to November a 9:00 AM Phoenix call is noon in New York, not 11:00 AM.

The Navajo Nation in northeastern Arizona does observe daylight saving, while the Hopi Reservation surrounded by it does not, so even within Arizona two clocks can apply. When someone writes "MST" in a summer invite, ask whether they mean Denver or Phoenix; the converter above uses Denver, and the time zone converter lets you pick other regions.

Wall Street opens at 9:30 AM Eastern, which is 7:30 AM in Denver and Salt Lake City, so traders, wealth managers and financial journalists in the Mountain zone start well before 8:00 AM. The closing bell at 4:00 PM Eastern rings at 2:00 PM Mountain, leaving a quiet late afternoon.

For companies with headquarters on the East Coast and offices in Denver or Utah's tech corridor, the shared working day is 9:00 AM–3:00 PM Mountain, or 11:00 AM–5:00 PM Eastern. A Denver-to-New York flight runs a little under four hours, so a 7:00 AM departure lands around 1:00 PM Eastern after the two-hour jump.