export declare function addDays(date: Date, days: number): Date;
export declare function differenceInCalendarDays(dateLeft: Date, dateRight: Date): number;
export declare function startOfDay(date: Date): Date;
export declare function endOfDay(date: Date): Date;
export declare function isWithinInterval(date: Date, interval: {
    start: Date;
    end: Date;
}): boolean;