Time zones

The same time in several time zones: for a meeting, a call or a release.

Time to convert

Time zone Time Day Offset Difference Actions

Good to know

Time zone names
The names are those of the IANA time zone database (Europe/Paris, America/New_York), used by every operating system. They name a city rather than an abbreviation: CST can mean Central America, China or Cuba, and an abbreviation does not say when summer time starts.
Summer time
The dates of the change differ between countries: the United States changes about three weeks before Europe in spring, and one week after in autumn. During those weeks, the difference between Paris and New York is 5 hours instead of 6. The southern hemisphere has its summer in January.
Half and quarter hours
Some offsets are not whole hours: India (+05:30), Nepal (+05:45), Newfoundland (-03:30), the Chatham Islands (+12:45).

Transparency

Everything is computed in your browser, by the scripts listed below. Nothing you type leaves this page.

Enforced by your browser
This page's Content Security Policy allows a single destination, the site's audience measurement (connect-src https://stats.r-no.fr, see below), and forbids any form submission (form-action 'none'), so even a bug could not send what you type anywhere. You can read the policy at the top of the page source.
Audience measurement
Like every page of the site, this one counts its visit with Umami, installed on R-no’s own server (stats.r-no.fr). It receives the address of the page, without parameters or anchor, the site you came from (its domain only), your browser, system, language and screen size, and the country, region and city deduced from your IP address, which is not kept. It never receives what you type, nor the result of the tool. No cookie, nothing stored in your browser; if your browser asks not to be tracked (Do Not Track), nothing is measured. The data is erased after 25 months.
  • /commun/mesure.js: the filter applied before each sending, written for R-no Toolbox. 1.4 kB
    SHA-256 225eec74fd12623d82fc05ee7d222be629ce454d081c129e8d1e249ed37ee716
  • https://stats.r-no.fr/m.js: Umami’s tracker, open source (MIT), served by the measurement server. Its fingerprint is not shown here: it changes with each version of Umami, and you cannot check from your browser that it is the published code. For that part, you have to trust R-no.
What is stored
No cookie, and nothing in the address. What you type is never stored: it disappears when you reload or close the page. Your language is given by the address itself (/en/ or /fr/): nothing is stored to remember it. Like any website, the server records the download of the page and its files in its access logs (IP address, date and time, address requested, browser name). It never receives what you type.
Code that runs here
  • app.js: the conversions and the page, written for R-no Toolbox. Not minified, no third-party library. 16.4 kB
    SHA-256 ff71c38ad8becd7aab094e0b514173e82fdb925712930a2dcbb8cfab94994b0f
  • textes.js: the French messages of the tool, shown by its script (the rest of the French page is written into its HTML when the site is built). It only defines texts, with no logic. 6.4 kB
    SHA-256 27b1f468fd9962b241faa12097b93bbfbcbdecf82ae2219d4a6885306eaaec55
  • /commun/langue.js: the language helper, the same on every page of the site. It reads the language of the page and gives the tool its messages in that language. It stores nothing. 1.6 kB
    SHA-256 80f76f69773ef628d36d09bf8387cfedebda4529210d7120649b6f5603310631
Where the rules come from
From your browser: it carries a copy of the IANA time zone database (through ICU) and gives it to the page with Intl.DateTimeFormat. The page downloads no rules and depends on no server. The flip side: an old browser may not know a recent change of rules (a country that drops summer time, for instance).
Your time zone
The page starts from the time zone of your device, which your browser gives it. It is only used for display: it is never sent or stored. The list of zones you add is forgotten when you leave the page.
How it was checked
Conversions were compared with GNU date and the system’s tz database on 2,000 moments between 1970 and 2037, in 12 time zones (including Kolkata, Kathmandu, Lord Howe and Chatham), and on every change of time in Paris, New York and Sydney from 2020 to 2030, hours skipped and repeated included. The tests run again before each release.
Check it yourself
Download a script and compare its fingerprint with the one above:
curl -s https://r-no.fr/dates/timezones/app.js | shasum -a 256
Limits
The rules are those of your browser’s copy of the tz database. Before 1970, the database is less reliable. Future times assume today’s rules stay in force. “Night” (10 pm to 7 am) is only an indication.