A timezone difference calculator uses IANA timezone data to determine the UTC offset for each selected city on a given date. It then compares the two offsets to calculate the exact time difference. Our tool also factors in Daylight Saving Time (DST) rules that vary by region and date, ensuring accurate results year-round. The visual timeline shows you exactly when work hours overlap, making it easy to schedule meetings across time zones.

Yes! Our calculator automatically accounts for DST transitions. By selecting a specific date, the tool checks whether each city observes DST on that date and adjusts the UTC offset accordingly. This is critical because DST start/end dates differ between countries — for example, the US and Europe change clocks on different dates, which can temporarily alter the time difference by one hour.

The best meeting hours are when both cities' typical work hours (9:00 AM – 5:00 PM) overlap. Our timeline highlights these overlaps in green. Generally, for US–Europe meetings, the sweet spot is 9:00 AM–12:00 PM Eastern Time (2:00 PM–5:00 PM in London). For US–Asia meetings, early morning (6:00 AM–8:00 AM Pacific) or late evening (7:00 PM–10:00 PM) often works best, though these fall outside standard work hours for one party. Use the timeline slider to find the optimal compromise.

The time difference can shift by one hour depending on whether one or both cities are observing Daylight Saving Time (DST). For instance, New York (UTC-5 standard / UTC-4 DST) and London (UTC+0 standard / UTC+1 DST) are normally 5 hours apart. But during the few weeks when one city has switched to DST and the other hasn't, the difference temporarily becomes 4 hours. By selecting a specific date, you see the exact difference for that day.

Yes! For recurring meetings, we recommend checking the time difference for several key dates throughout the year, especially around DST transitions (March and November for most regions). Some teams choose a fixed UTC time for recurring meetings to avoid confusion. Our tool can help you identify a UTC time that works reasonably well year-round, even if it occasionally falls slightly outside ideal work hours for some participants.

Our calculations use the IANA Time Zone Database (tzdata), the same authoritative source used by operating systems, smartphones, and servers worldwide. This database is continuously updated to reflect changes in timezone rules, DST policies, and historical data. The tool leverages your browser's built-in Intl API, which provides up-to-date timezone information. For the most accurate results, ensure your browser and operating system are updated.

The 24-hour timeline visualizes work-hour overlaps at a glance. Green blocks indicate hours when both cities are within typical work hours (9:00 AM – 5:00 PM) — these are ideal for meetings. Blue shows when only City 1 is working, purple when only City 2 is working, and gray when both are outside work hours. Drag the slider to see exact times for both cities at any point in the day.

You can take a screenshot of the timeline and time cards to share. For a more precise approach, note the times in both timezones — for example: "Let's meet at 10:00 AM EST (3:00 PM GMT)." Many teams also use calendar tools like Google Calendar or Outlook, which automatically handle timezone conversions when you invite participants from different locations. Our tool helps you identify those times before sending the invite.

This tool is optimized for comparing two cities, which covers the most common use case: one-on-one meetings or calls between two locations. For multi-city comparisons, we recommend using a world clock tool or checking multiple pairs sequentially. Start with the two most distant timezones in your group — if you can find a time that works for both extremes, it usually works for everyone in between.

Common timezone abbreviations: EST = Eastern Standard Time (UTC-5), EDT = Eastern Daylight Time (UTC-4), GMT/BST = Greenwich Mean Time / British Summer Time (UTC+0 / UTC+1), CET/CEST = Central European Time (UTC+1 / UTC+2), IST = India Standard Time (UTC+5:30), JST = Japan Standard Time (UTC+9), AEST = Australian Eastern Standard Time (UTC+10), PST/PDT = Pacific Standard/Daylight Time (UTC-8 / UTC-7). Our tool shows the current abbreviation and UTC offset for each selected city.