export interface LocaleVocab {
    monthLong: string[];
    monthShort: string[];
    weekdayLong: string[];
    weekdayShort: string[];
    dayPeriod: string[];
}
export declare function subscribeToVocabChanges(listener: () => void): void;
/**
 * Supply a custom month/weekday/day-period vocabulary for a locale key,
 * overriding the Intl-derived vocab this library would otherwise build
 * for that key. Useful for locales Intl doesn't cover well — the
 * Parsing section of the README ("MMMM/MMM assume a 12-month calendar")
 * calls out the Hebrew leap-month gap as a specific case this addresses.
 *
 * Throws descriptively on malformed input (wrong array lengths, empty
 * strings, duplicate entries, missing fields) rather than failing later
 * during format/parse.
 *
 * Registered vocab takes precedence over the Intl-derived vocab for that
 * locale key, including for already-cached entries — registering
 * invalidates the prior cache entry for that locale so the next call
 * picks up the new vocab.
 *
 * @example
 * registerLocaleVocab('en-u-ca-hebrew-leap', {
 *   monthLong: ['Nisan','Iyar','Sivan','Tammuz','Av','Elul','Tishrei','Marcheshvan','Kislev','Tevet','Shevat','Adar I','Adar II'],
 *   monthShort: ['Nis','Iyy','Siv','Tam','Av','Elu','Tish','Chesh','Kis','Tev','Shv','Ad1','Ad2'],
 *   weekdayLong: ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday'],
 *   weekdayShort: ['Mon','Tue','Wed','Thu','Fri','Sat','Sun'],
 *   dayPeriod: ['AM','PM'],
 * });
 */
export declare function registerLocaleVocab(locale: string, vocab: Partial<LocaleVocab>): void;
export declare function normalizeLocaleTag(locale: string): string;
export declare function canonicalCacheKey(locale: string): string;
export declare function assertValidLocaleTag(locale: string): void;
export declare function partValue(formatter: Intl.DateTimeFormat, date: Date, type: Intl.DateTimeFormatPartTypes): string;
export declare function getCustomVocab(locale: string): LocaleVocab | undefined;
export declare function getLocaleVocab(locale: string): LocaleVocab;