/**
 * 判断是否日期对象
 * @param date
 * @returns date is Date?
 */
export declare function isDate(date: unknown): date is Date;
/**
 * 判断是否为合法日期对象
 * @param date
 * @returns is a valid date object?
 */
export declare function isValidDate(date: unknown): boolean;
declare const formatMap: {
    yyyy: (date: Date) => number;
    yy: (date: Date) => string;
    MM: (date: Date) => string;
    M: (date: Date) => number;
    dd: (date: Date) => string;
    d: (date: Date) => number;
    HH: (date: Date) => string;
    H: (date: Date) => number;
    hh: (date: Date) => string;
    h: (date: Date) => number;
    mm: (date: Date) => string;
    m: (date: Date) => number;
    ss: (date: Date) => string;
    s: (date: Date) => number;
    a: (date: Date) => "上午" | "下午";
    Q: (date: Date) => number;
    w: (date: Date) => string;
};
export type DateFormatKey = keyof typeof formatMap;
/**
 * 将日期对象格式化为自定义字符串
 * @param {Date} date 日期对象
 * @param {string} format 格式字符串（如 "yyyy年MM月dd日", 默认为'yyyy-MM-dd'）
 * @returns {string} 格式化后的日期字符串
 *
 * @example
 * // 今天是2025年1月8日
 * formatDate(new Date(), '今天是yyyy年M月d日')
 *
 * @example
 * // Today: 2025/1/8
 * formatDate(new Date(), 'To{d}{a}y: yyyy/M/d')
 */
export declare function formatDate(date: Date, format?: string): string;
export {};