Time zones
Time Zone Overlap — When Two Countries Are Awake Together
Pick two countries, set working hours, and see exactly when both are at their desks — every window in local time, DST resolved on the day itself by the standard Intl API. The closest-compromise pair is included when the working days never touch.
Loading time zones…
Overlap windows
No overlap during these working hours.
No overlap during these hours
The working days don't touch. Closest compromise — the moment with the least total time outside working hours:
China 19:30–19:45China is 90 min outside its hoursUnited States 07:30–07:45United States is 90 min outside its hours180 min total compromise
Computed for 2026-09-02 · DST as in effect that day, resolved by your browser's Intl data
The day at a glance
Strips show each country's LOCAL time, 00:00–24:00.
How this tool works
- Pick two countries — add a third if you like. Each side gets a time zone: multi-zone countries (the United States, Russia, Mexico…) preselect a representative zone you can switch with one click.
- Set the working hours with the two sliders — the default 9:00–18:00 local, adjustable in 15-minute steps, applied to every side in ITS OWN local clock.
- The tool scans the selected day in 15-minute steps and lists every continuous window where all sides are inside working hours at once — each window labeled with the local times on both sides, e.g. “Beijing 16:00–18:00 ⇄ Berlin 09:00–11:00”.
- The two 24-hour strips show the same picture at a glance: one strip per country in its local time, working hours shaded, overlap highlighted. No overlap? You get the closest pair instead — the instant where the total compromise (minutes outside working hours, summed over all sides) is smallest.
The selected countries and working hours live in the URL (?a=china&b=united-states-of-america&hours=9-18), shareable, indexable URL-as-state (D4).
Data & method
Time zones come from the IANA Time Zone Database, repackaged by the MIT-licensed @vvo/tzdb library and frozen at build time as zone NAMES only — this page stores no UTC-offset constants. Every offset (and every DST shift) is computed in your browser at view time with the standard Intl API for the exact date you are looking at, so the answer follows the current daylight-saving rules your own runtime ships, including a DST transition that falls on the day you scan. Multi-zone countries get a curated representative zone (the capital's zone, or the largest metro's — New York for the United States, Sydney for Australia, Moscow for Russia) that you can switch away from; single-zone countries have nothing to choose. The computation is a pure minute-scan shared by this page, the embeddable view and the GlobeVS MCP tool, so all three surfaces answer identically.
The scan itself is a JavaScript enhancement — without it you can still read the guide, the data note and the FAQ, and the panel above shows a worked example computed at build time for its own date.
Sources
Embed this tool
Add the overlap calculator to your own site: paste the snippet below into your HTML and it loads the same interactive tool inside an iframe, with a small non-removable “Powered by” attribution link back to this page. The embed is available in English.
<iframe src="https://globevs.com/embed/timezone-overlap" width="800" height="600" title="Time Zone Overlap — GlobeVS" loading="lazy" style="border:0;max-width:100%" sandbox="allow-scripts allow-same-origin allow-popups"></iframe>FAQ
How is daylight saving time (DST) handled?
DST is never stored — it is computed. The page freezes only IANA zone names; when you open the tool, your browser's standard Intl timezone data resolves each zone's offset for the exact day being scanned, transitions included. If a DST change happens on that day, the overlap windows shift or split exactly the way the local clocks did. The tool always scans today (your local date), so the answer you get is the answer for the day you will actually make the call.
Countries like the United States or Russia span many time zones — which one is used?
Of the 176 countries in the dataset, 19 span more than one IANA zone. Each gets a curated representative zone by default — the capital's zone where the capital has one (Moscow, Mexico City, Madrid), otherwise the largest metro's (New York, Toronto, Sydney) — shown as chips above the results, so you can switch to any other zone of that country in one click before comparing. The remaining countries all run on a single zone, where there is nothing to choose.
Why country level — no city-by-city meeting planner?
GlobeVS is a country-comparison site: every tool answers questions about countries, from true size to distances to the zones covered here. A city-level meeting planner is a different (and brutally well-served) product; a two- or three-country overlap strip — “can Beijing and Berlin talk at reasonable hours?” — is the question this tool answers cleanly, including the representative-zone choice for multi-zone countries that city tools usually hide.
China and the United States show no overlap during 9:00–18:00 — is that wrong?
It is correct, and it is the honest headline: their working days barely touch (13 hours apart in winter, 12 in summer). When nothing overlaps, the tool shows the closest pair instead — the moment where the total compromise, summed over all sides as minutes outside working hours, is smallest. For China and the US East Coast that lands around Beijing 08:00 ⇄ New York 19:00: each side gives up about an hour. Widen the sliders (for example 06:00–20:00) and real windows appear.
Where does the time zone data come from?
From the IANA Time Zone Database (tzdata) — the public-domain reference the world's computers sync on — repackaged by the MIT-licensed @vvo/tzdb library (238 zones across the 176 countries here) and frozen into this site at build time. Country boundaries and slugs come from Natural Earth (public domain) with metadata from mledoze/countries (ODbL). Offsets and DST come from your own browser's Intl data at view time; nothing on this page can drift out of date with a stored table.
Related
Put the two countries side by side across 46 indicators in Country Compare →
Time difference is one thing, physical distance another — measure it in the Country Distance tool →