export declare function addDays(date: Date, days: number): Date;
export declare function addMonths(date: Date, months: number): Date;
export declare function addYears(date: Date, years: number): Date;
export declare function isWeekend(date: Date): boolean;
export declare function getFirstDayOfWeek(date: Date): Date;
export declare function getWeekNumber(year: number, month: number, day: number): number;
export declare function isLeapYear(year: number): boolean;