EST to PST: Eastern to Pacific Time

The Earth turns 360° in 24 hours, or 15° per hour, so the standard zones were drawn around meridians that are multiples of 15°. Eastern Standard Time is the mean solar time of 75°W, a line that runs just east of Philadelphia. Pacific Standard Time is the mean solar time of 120°W, the meridian California's 1850 constitution set as its eastern border north of Lake Tahoe. 120 − 75 = 45 degrees, and 45 ÷ 15 = 3 hours. The same arithmetic puts Mountain Time on 105°W and Central Time on 90°W, which is why Mountain Time is 2 hours behind ET and Central Time 1 hour behind.

American railroads adopted these zones on November 18, 1883, replacing dozens of local railroad times, and the Standard Time Act of 1918 made them federal law. Because the big cities on both coasts sit close to their zone's meridian, the clock tracks the sun well on each side. On January 15, 2027 the sun is highest at 12:05 PM in New York and 12:02 PM in Los Angeles. Seattle, more than 2° west of 120°W, has to wait until 12:19 PM.

Daylight saving time begins and ends at 2:00 AM local time in each zone, not at one instant across the country. Eastern Time switches first and Pacific Time three hours later, so for three hours on each transition night the coasts are on different halves of the rule:

• Spring: New York moves to EDT at 07:00 UTC while Los Angeles stays on PST until 10:00 UTC. For those three hours the gap is 4 hours.
• Autumn: New York returns to EST at 06:00 UTC while Los Angeles stays on PDT until 09:00 UTC. For those three hours the gap is 2 hours.

The windows fall overnight, so they never touch office hours, but they do catch scheduled jobs. A backup scheduled for 12:30 AM PT normally runs at 3:30 AM ET; on March 14, 2027 it runs at 4:30 AM ET and on November 7, 2027 at 2:30 AM ET. Systems that must stay in lockstep are usually scheduled in UTC, as explained on the EST to UTC page.

With a 9-to-5 day on both coasts, the overlap is five hours: 12:00 PM–5:00 PM ET, which is 9:00 AM–2:00 PM PT. In practice it is shorter, because the East Coast lunch hour lands at 9:00 AM Pacific and the West Coast lunch hour lands at 3:00–4:00 PM Eastern. The most reliable slot is 1:00–3:00 PM ET (10:00 AM–12:00 PM PT): both sides are settled in and nobody is at lunch.

Fixed East Coast schedules land early in the West. The NYSE opening bell at 9:30 AM ET rings at 6:30 AM PT, and the 4:00 PM close is 1:00 PM PT (see stock market hours). TV networks delay the Pacific feed so prime time starts at 8:00 PM on both coasts, but live events such as election-night results air at the same instant everywhere.