import { DateString, MarkedDays } from '../types';
export declare function isYear(year: number): boolean;
export declare function isValidDate(str: string): str is DateString;
export declare function leapYear(year: number): boolean;
export declare function isLeapYear(year: number): boolean;
export declare function changeMarkedDays(markedDays?: MarkedDays, nextMarkedDays?: MarkedDays): boolean;