Time Zone Overlap Calculator
Finally, find the one hour where New York, London, and Tokyo are all awake without using a spreadsheet. This timezone overlap calculator lets you add 3+ cities and instantly highlights the "green zone" where working hours overlap perfect for scheduling global meetings, coordinating remote teams, or finding the best time to reach international clients. No mental math required. Free, no signup. It helps you move from guesswork to a confident decision with clear inputs and readable output. Adjust values, compare scenarios, and share results quickly. Runs client-side in your browser, with no signup required. Built for speed, clarity, and repeat use. Method details for Timezone Overlap Calculator: The result model exposes each formula and equation, applies deterministic calculation steps, uses explicit decimal rounding, and keeps unit assumptions visible so outputs are auditable.
Uses today if blank. Set a future date for accurate DST handling.
🌍 Overlap Windows
How to Use This Tool
- Step 1 - Select 2 or more cities from the dropdown (e.g., New York, London, Tokyo)
- Step 2 - Set your standard work hours (default: 9 AM - 5 PM local time)
- Step 3 - Click 'Find Golden Hour' to see all overlapping hours with local times for each city
Why This Tool?
Coordinating across time zones is mentally exhausting. Most tools show clocks side-by-side, forcing you to manually calculate overlaps. This tool uses JavaScript Intl API to automatically detect working hour overlaps across unlimited cities.
The calculator converts your local work hours (e.g., 9 AM - 5 PM) into each city's timezone, then finds hours where all cities are within their work windows. Perfect for remote teams, digital nomads, or anyone scheduling international calls.
Pro tip: If no overlap exists, try expanding work hours to 8 AM - 6 PM or consider asynchronous communication. For US-Asia calls, early morning or late evening slots typically work best.