Birthday Across Timezones

Timezone Studio is a small, independent utility site built for people whose work, family, or business genuinely spans more than one timezone. We are not a generic "date calculator" portal — every tool here is written for a specific, recurring real-world problem (scheduling meetings, surviving jet lag, planning deployments, picking wedding times, fitting crypto trades into overlapping liquidity windows, and so on).

What this site is good at. Visualising multiple cities side by side, flagging Daylight Saving transitions before they bite you, and giving you a defensible "least-bad" answer when no slot is perfect for everyone. The data behind every page is your browser's own Intl timezone database (the same source used by V8/JavaScriptCore and modern browsers), so DST shifts are honoured as they actually happen in your locale — not a stale snapshot.

What this site is NOT. It is not an authoritative source for trading windows, exchange opening hours, or holiday calendars. Stock and crypto exchange hours in particular change without notice, and we cannot guarantee the matrix on the Stock Market Hours tool is up to date at the second you read it — always re-check the exchange's own announcement before sizing a position. The Jet Lag planner is a rough heuristic based on the direction of travel and the number of zones crossed, not a medical recommendation. The Health Risk estimator surfaces a single number from population-level research; treat it as a conversation starter, not a diagnosis.

Who built it. A small team of remote engineers and writers who have, between us, shipped across at least nine timezones and lost track of how many meetings were re-scheduled because someone forgot Europe had already switched off summer time. We publish what we would actually use ourselves.

Limitations. Because every calculation happens in your browser, the tool reflects the timezone rules known to your browser at load time. If a country changes its DST policy mid-year (Brazil, Morocco, Egypt and a handful of others have done this in the past), the new rule may take a few weeks to reach your browser via OS updates. The site does not collect, store, or transmit your inputs anywhere.

Short version. We do not collect, store, sell, or share any personal data you enter into these tools. All calculations run locally in your browser. The site uses a small number of third-party services, listed below, that may set cookies or read identifiers for their own purposes.

Data we do not collect. The city selections, dates, working hours, jet-lag preferences and any other values you type into a tool on this site are processed entirely by JavaScript running on your device. They are never sent to a server we operate, never logged, never aggregated, and never used to build a profile of you.

Cookies. We do not set any first-party cookies. We do not use any local-storage based fingerprinting. The only client-side storage we use is a per-page toggle (for example, the mobile navigation open/closed state) that lives in memory only and is discarded when you close the tab.

Third-party advertising — Google AdSense. Pages on this site may display ads served by Google AdSense. AdSense uses cookies to serve ads based on a user's prior visits to this site or other sites on the open web. Google's use of advertising cookies enables it and its partners to serve ads based on the visit to this site and/or other sites. Users may opt out of personalised advertising by visiting Google Ads Settings. You may also opt out of certain third-party vendors' use of cookies for personalised advertising by visiting www.aboutads.info.

Third-party cookies / vendors. When AdSense loads, the Google advertising products may set or read cookies, the DoubleClick cookie, or other identifiers as described in Google's advertising policies. Some of our advertising partners may use the DART cookie to serve ads to you based on your visit to this site and other sites on the Internet. You may decline the DART cookie by following the link in that policy page.

Analytics. If we add analytics at a later date, we will use a privacy-respecting tool (Plausible or self-hosted Umami) that does not require consent banners under GDPR. If that changes, this page will be updated before any new tracking loads.

Children. This site is not directed at children under 13 and we do not knowingly process any data of minors.

Changes. Any material change to this policy will be reflected here with a new "last updated" date at the top of this section. Continued use of the site after a change constitutes acceptance.

Contact. Questions about this policy can be sent to the address listed on our About section. We aim to reply within 14 days.

The information and tools provided on Timezone Studio are for general informational and planning purposes only. They do not constitute professional, financial, medical, legal, or trading advice, and should not be relied upon as a substitute for consultation with a qualified professional.

No warranty. We make every effort to keep the tools accurate, but timezone rules change (countries abolish or shift DST, redefine their standard offset, or change exchange hours with little notice). We provide the tools "as is" and "as available", without any warranty of any kind, express or implied, including without limitation warranties of merchantability, fitness for a particular purpose, or non-infringement.

Financial tools. The Stock Market Hours and Crypto Trading Window tools are designed as planning aids, not as trading signals. They do not constitute a recommendation to buy, sell, or hold any security or cryptocurrency. Past performance is not indicative of future results.

Health tools. The Jet Lag Recovery Planner and Timezone Health Risk estimators are coarse heuristics based on published population research. They are not medical devices, do not diagnose any condition, and must not be used to make decisions about medication, treatment, or when to seek medical care.

Third-party content. The site may link to external sites (exchange homepages, government holiday calendars, official timezone databases). We are not responsible for the content, accuracy, or practices of those third-party sites.

Limitation of liability. To the maximum extent permitted by applicable law, in no event shall the site authors, contributors, or affiliates be liable for any indirect, incidental, special, consequential or punitive damages, or any loss of profits or revenues, whether incurred directly or indirectly, or any loss of data, use, goodwill, or other intangible loss, resulting from your use of the site.