World Clock & Time Zone Converter
Compare time across world cities in real-time. Slide to convert time zones instantly. Auto DST detection.
About This Tool
The World Clock displays the current time in multiple cities and time zones simultaneously, with easy conversion between any two zones. It is invaluable for remote teams coordinating across time zones, international travelers planning calls, and businesses managing global operations.
Sat, May 9, 2026 Β· UTC-7 Β· βοΈ DST
β±οΈ Time & Date Control
Click "Adjust Time" to drag the slider and all city times update simultaneously. Change the date to check DST status for any day.
Sat, May 9, 2026
Sat, May 9, 2026
Sat, May 9, 2026
Sun, May 10, 2026
Sun, May 10, 2026
How to Use
- Check the base city time at the top and compare real-time clocks for all added cities below.
- Click "Adjust Time" and drag the slider to convert all city times simultaneously. You can also change the date.
- Click "Change Base" to switch the reference city to any city you prefer.
- Click "Add City" to add up to 10 cities from 150+ worldwide locations. Search in any language.
- Use "Find Meeting Time" to see overlapping business hours across all cities. Adjust work hours or enable flex mode.
- Drag cards to reorder. Your city selection and base city are automatically saved.
Frequently Asked Questions
Does this world clock support Daylight Saving Time (DST)?
Yes, DST is automatically detected based on the selected date. Cities currently in DST display a 'βοΈ DST' badge. Change the date to check DST status for any day of the year.
What is the time difference between Korea and the US?
Korea (KST, UTC+9) is 14 hours ahead of US Eastern Time (EST, UTC-5), or 13 hours during DST. The difference with Pacific Time (PST) is 17 hours, or 16 during DST.
Can I change the base/reference city?
Yes, click the 'Change Base' button at the top to select any city as your reference. The slider and time differences will adjust accordingly.
The meeting finder shows no overlapping hours.
For cities with large time differences (e.g., US and Korea), standard 9-18 business hours don't overlap. Enable 'Flex hours (7AM-10PM)' or widen the work hour range. When no overlap exists, the nearest time is shown in orange.
How many cities can I add?
You can add up to 10 cities from over 150 worldwide locations. Search by name in any language.
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How It Works
The World Clock leverages the JavaScript Intl.DateTimeFormat API and the IANA Time Zone Database (also known as the tz database or Olson database). Each timezone is identified by a region/city string (e.g., "America/New_York", "Asia/Seoul") and has defined rules for UTC offset and Daylight Saving Time (DST) transitions.
Time conversion between zones is performed by first converting the source time to UTC (Coordinated Universal Time), then applying the target zone's offset. For example, converting 3:00 PM KST (UTC+9) to EST (UTCβ5 or UTCβ4 during DST): 15:00 β 9 hours = 06:00 UTC, then 06:00 β 5 hours = 01:00 AM EST.
The clock updates every second using requestAnimationFrame to stay synchronized with the system clock. DST transitions are handled automatically by the browser's Intl API, which references the operating system's timezone data. This ensures accurate time display even during spring-forward and fall-back transitions.
Related Articles
It's 3 PM in Seoul β What Time Is It in New York? World Clock Cheat Sheet
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2026-03-18The Seoul-New York Meeting That Only Works at 8 AM KST β Time Zone Math in 2026
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