/**
 * `@platform-modules/util/datetime` — civil-date resolution in an IANA time zone.
 *
 * Pure `Intl` (zero-dep, Workers-safe). This leaf answers exactly one question:
 * "what calendar date is this instant, in this zone?" — no display formatting
 * (that is `@platform-modules/i18n/format`'s axis), no `util/timezone` import
 * (so an R-only consumer tree-shakes the validation leaf away).
 *
 * The inverse (civil wall-time → instant, via a DST offset-fixpoint) is a designed-next
 * sibling, not yet built — adding it here later is non-breaking.
 */
/** Thrown when `instant` is not a valid `Date` (e.g. `new Date('nope')`). */
declare class InvalidInstantError extends Error {
    constructor();
}
/** Thrown when `zone` is not a runtime-recognized IANA time zone. */
declare class InvalidTimeZoneError extends Error {
    constructor(zone: string);
}
/**
 * The civil calendar date (`YYYY-MM-DD`) that `instant` falls on in `zone`.
 *
 * Uses the production-proven, pinned `en-CA` locale with explicit numeric fields → ISO order,
 * zero-padded, Gregorian, Latin digits on every runtime. Validate at the trust boundary:
 * a non-valid `Date` or unknown zone throws, never returns a wrong / `Invalid Date` string.
 */
declare function civilDateInZone(instant: Date, zone: string): string;

export { InvalidInstantError, InvalidTimeZoneError, civilDateInZone };