export type StartOfUTCKey = 'year' | 'quarter' | 'month' | 'week' | 'week_sun' | 'week_mon' | 'week_tue' | 'week_wed' | 'week_thu' | 'week_fri' | 'week_sat' | 'day' | 'hour' | 'minute' | 'second' | 'millisecond';
/**
 * Sets the provided date to start of UTC of provided key
 *
 * @param {Date|string} val - Date to set to start of
 * @param {StartOfUTCKey} key - (default='millisecond') Key to set
 */
declare function startOfUTC(val: Date | string, key?: StartOfUTCKey): Date;
export { startOfUTC, startOfUTC as default };