EST to ChST Converter

At 12:00 PM EST on January 15, it's already 3:00 AM the next day in Guam. ChST runs 15 hours ahead of Eastern Standard Time. That gap is fixed between the two abbreviations, because Chamorro Standard Time never changes its clocks while Eastern Time shifts between EST (UTC−5) and EDT (UTC−4) for daylight saving.

Why is ChST always 15 hours ahead of EST?

ChST (Chamorro Standard Time, UTC+10) sits exactly 15 hours ahead of EST (Eastern Standard Time, UTC−5). Not roughly. Not usually. The offset between these two specific abbreviations is fixed at 15 hours, every day of the year.

EST is the winter clock for the US Eastern Time Zone. ChST is the year-round time for Guam and the Northern Mariana Islands. Those territories observe no daylight saving at all. So the abbreviation pair EST→ChST never moves.

When does the EST to ChST gap drop to 14 hours?

Eastern Time doesn't stay on EST all year. From the second Sunday in March through the first Sunday in November, the Eastern zone switches to Eastern Daylight Time (EDT, UTC−4). During that window, ChST is only 14 hours ahead of Eastern Time.

The change happens at 2:00 AM local time on these dates:

  • 8 March 2026: clocks spring forward, EST → EDT
  • 1 November 2026: clocks fall back, EDT → EST
  • 14 March 2027: clocks spring forward, EST → EDT
  • 7 November 2027: clocks fall back, EDT → EST

Guam's clocks don't move. Pacific/Guam stays on ChST, UTC+10, in 2026 and 2027 alike.

How do I schedule a call from EST to ChST?

The 9:00 AM to 5:00 PM working days do not overlap at all. Not when the gap is 15 hours. Not when it's 14. One side is always asleep.

Book one of these windows instead:

  • Late afternoon from Eastern Time: call at 4:00 PM to 5:00 PM EST. You'll reach Guam at 7:00 AM to 8:00 AM the next morning.
  • Early morning from Eastern Time: call at 6:00 AM to 7:00 AM EST. That hits 9:00 PM to 10:00 PM in Guam, if the Guam side can stay late.
  • Skip the standard workday overlap: it doesn't exist. Someone shifts their hours.

Should I write EST, EDT, or ET when converting to ChST?

Use "EST" only when you mean the fixed UTC−5 standard time, roughly November through early March. Use "EDT" for the summer clock. Use "ET" (Eastern Time) when you're not sure which one applies: it's the correct year-round label.

Writing "EST" in July is the most common mistake. It puts you off by an hour. With a 14-hour gap already, that hour pushes a call from late night to the middle of the night in Guam.