export declare function isLeapYear(year: number): boolean;
export declare function addDays(date: Date, n: number): Date;
export declare function addMonth(date: Date, n: number): Date;
export declare function isSameYear(date1: Date | null, date2: Date | null): boolean;
export declare function isSameMonth(date1: Date | null, date2: Date | null): boolean;
export declare function isSameDay(date1: Date | null, date2: Date | null): boolean;
export declare function clampDate(min: Date | null, date: Date, max: Date | null): Date;