Interface languages

The web interface is available in English and Simplified Chinese. The language control is available on sign-in, account and standalone public booking pages. Changing it updates the existing page without restarting a form, discarding a chosen time, reissuing a booking or replacing its private management link.

An explicit interface choice takes precedence over a supported signed-in profile default, then the browser’s supported language, then English. Signed-in routes read the existing profile after authentication; public routes never request a session or profile to choose a language. The interface choice is separate from the profile’s Language BCP 47 field: changing the interface never saves the profile. A supported profile default is loaded when the authenticated account becomes available. Unsupported profile locale values remain valid profile settings.

Without an explicit interface choice, date and time formatting retains the browser’s full BCP 47 locale, including locales whose interface text falls back to English. Choosing English or Simplified Chinese explicitly also chooses that display format. Dates retain the Gregorian calendar and the selected IANA time zone. A booking flow freezes its request locale independently of display changes, so retrying after a lost response keeps the same body and idempotency key.

The language preference stores only the tiny allowlisted value en or zh-CN, under hourmere-language in local storage and a same-name SameSite=Lax, path-wide cookie. The cookie has a one-year lifetime and is Secure on HTTPS. Refusing either storage mechanism does not prevent changing the current page. No account identifiers, answers or management capabilities enter preference storage. The standalone email sign-in confirmation page uses the same preference cookie, then Accept-Language, and provides its own language buttons. Language changes never submit that form or change its fragment.

Public booking and rescheduling pages also remember an explicitly selected IANA time zone in local storage. A valid saved choice becomes the default on later booking-page visits; browser detection alone does not save a preference. Each manage link starts in that booking’s stored invitee zone, matching its emails, or the browser zone if the stored zone is unavailable. A choice made on the manage page applies for that view and future booking-page visits. The picker still includes the browser’s zone. Blocked storage does not prevent choosing a zone for the current visit. Individual booking pages show the host’s profile zone and, when the selected instant has a different local time in that known zone, the meeting time for the host. Round-robin pages wait until a host is assigned.

User-provided event titles, descriptions, names, answers, locations and question options are left as entered. Known error codes have fixed local messages. Unknown server prose is shown verbatim rather than interpreted as a translation key. API, MCP and CLI machine protocols, notification email templates, website and legal pages are outside this interface translation catalog.

Widgets

The standalone helper accepts an optional, strictly validated language value in initInline and openPopup, or data-hourmere-language on declarative elements. Only en and zh-CN are accepted. Without an explicit value, the helper uses the host page’s supported <html lang>, then a supported browser language, then English. Embedded pages hide their page-level language picker; choose the page or widget language before initialization. The iframe receives only that non-sensitive allowlisted value in its language query parameter. Existing exact origin, source and instance checks still apply; completion messages contain no booking or attendee data.

Development

apps/web/src/i18n/common.ts contains public/shared message keys and Simplified Chinese text. The separate admin.ts catalog is registered only through the existing lazy session graph. English text is the typed semantic key. Use t(key, values) during render and msg(key, values) for a notice or validation message held in state. Nested messages, date arguments and lists are formatted when rendered, so an already visible message follows a language change. Plain interpolation arguments remain literal user content. Wrap arbitrary server prose or user-generated page titles in literal(text).

Do not translate protocol fields, create language-based React keys, replace arbitrary DOM text, add private session lookups to public routes, or include capabilities in language parameters or preferences. Test both languages and preserve the existing arbitrary-locale, Gregorian, daylight-saving and privacy regressions when adding pages.