/**
 * Get the number of full years between the given dates.
 *
 * @param {Date} dateLeft
 * @param {Date} dateRight
 *
 * @return {number}
 */
export declare const diffInYears: (dateLeft: Date, dateRight: Date) => number;
/**
 * Calculates the Luhn checksum of a string of digits.
 *
 * @param {string|number} str
 *
 * @return {number}
 */
export declare const luhn: (str: string) => number;
/**
 * Test if the input parameters are a valid date or not.
 *
 * @param {int} year
 * @param {int} month
 * @param {int} day
 *
 * @return {boolean}
 */
export declare const testDate: (year: number, month: number, day: number) => boolean;