A clear explanation of UTC offsets, daylight saving time, and how the same place can shift by one hour seasonally.

This guide focuses on practical steps you can use immediately—whether you’re scheduling a call, planning travel, or publishing a time on a website.

What this article covers

You’ll learn a repeatable approach that works across US states, countries, and DST transitions. The goal is simple: never guess and never rely on memory for offsets.

The safest way to communicate time

When you publish time for other people:

  • Include the date (not just the time).
  • Include the time zone.
  • Use a 24-hour clock or AM/PM with a clear label.
  • If your audience spans regions, include a second reference zone.

When you schedule time for systems, store it as:

  • timestamp + IANA timezone (or timestamp in UTC).

Troubleshooting checklist

  • Is your device time zone set correctly?
  • Are you looking at the right date after conversion?
  • Does either location observe DST?
  • Are you mixing abbreviations (EST) with IANA zones (America/New_York)?
  • For recurring meetings: did DST change since the last meeting?

Frequently asked questions

  • Do I need to include the date as well as the time? Yes—especially when conversions cross midnight.
  • Is an abbreviation like “EST” always correct? Not always. Prefer ET or an IANA time zone name.
  • What’s the fastest way to confirm accuracy? Open a converter and verify with the time zone name, not just the offset.

Quick checklist you can use today

  • Write the date and time together.
  • Add a time zone label.
  • For international audiences, add a second zone or a converter.
  • Re-check around DST weeks.
  • For recurring events, let calendars handle conversion when possible.