/**
 * `@platform-modules/util/timezone` — IANA time-zone validation + listing.
 *
 * Pure `Intl` (zero-dep, Workers-safe). For per-user / per-tenant zone selection in
 * global / multi-region apps: narrow an arbitrary string at the trust boundary, enumerate
 * the runtime's zones, group them for a picker. No host default is baked in — `UTC` is the
 * neutral listing fallback, never a policy choice (any host-specific default is intentionally
 * stripped — zone defaults are host policy, not module policy).
 */
/** A string proven to be a runtime-recognized IANA time zone (narrowed by `isValidTimezone`). */
type IanaTimezone = string & {
    readonly __brand: 'IanaTimezone';
};
/** The neutral zero-offset zone — the listing fallback, never a host's chosen default. */
declare const UTC: IanaTimezone;
/**
 * Narrow an arbitrary string to `IanaTimezone`. Trust-boundary validator: a zone string
 * from a user / API is unsafe until this returns true. Empty → false; unknown zone → false.
 */
declare function isValidTimezone(tz: string): tz is IanaTimezone;
/**
 * All IANA zones the runtime supports, sorted ascending. Memoized + frozen — the set is
 * static per runtime, so the `Intl.supportedValuesOf` call + sort run once and the returned
 * snapshot is immutable (mutate a copy). Falls back to `[UTC]` where `supportedValuesOf` is absent.
 */
declare function listSupportedTimezones(): readonly IanaTimezone[];
/**
 * Group zones by IANA continent prefix (`Europe/Paris` → `Europe`); a zone with no `/`
 * (e.g. `UTC`) lands in `Other`. For rendering a grouped zone-picker.
 */
declare function groupTimezonesByContinent(zones: readonly IanaTimezone[]): Record<string, IanaTimezone[]>;

export { type IanaTimezone, UTC, groupTimezonesByContinent, isValidTimezone, listSupportedTimezones };