/**
 * Retrieves the number of days in the month of the given date.
 *
 * @example
 * daysInMonth("2024-02-01") // 29 (leap year)
 * daysInMonth("2023-02-01") // 28
 *
 * @param date The date to check. Defaults to the current date.
 * @returns The number of days in the month.
 */
export declare function daysInMonth(date?: Date | string | number | null): number;