export type DiffKey = 'week' | 'weeks' | 'day' | 'days' | 'hour' | 'hours' | 'minute' | 'minutes' | 'second' | 'seconds' | 'millisecond' | 'milliseconds';
/**
 * Compute the diff between two dates in the provided key
 *
 * @param {Date|string} val_a - Date to diff against
 * @param {Date|string} val_b - Date to diff with
 * @param {DiffKey} key - (default='millisecond') Key to diff in
 */
declare function diff(val_a: Date | string, val_b: Date | string, key?: DiffKey): number;
export { diff, diff as default };