import type { CustomSyntaxChecker } from '../../types.js';
/**
 * Validates a datetime string against all WHATWG date and time formats.
 *
 * Tries each format (date, time, month, yearless date, local/global date-time,
 * time-zone offset, week, year, and duration strings) and returns the best match.
 *
 * @see https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#dates-and-times
 */
export declare const checkDateTime: CustomSyntaxChecker;