/**
 * Checks whether the given value is a valid `Date` object.
 *
 * @example
 *   isValidDate(new Date()); // true
 *
 * @example
 *   isValidDate(new Date("not-a-date")); // false
 *
 * @example
 *   isValidDate("definitely-not-a-date"); // false
 */
export declare const isValidDate: (date: unknown) => date is Date;
/**
 * @example
 *   dateToISOString(new Date("2025-10-16T11:01:09.564Z", "date")); // "2025-10-16"
 *
 * @example
 *   dateToISOString(new Date("2025-10-16T11:01:09.564Z", "datetime-utc")); // "2025-10-16T11:01:09.564Z"
 *
 * @example
 *   dateToISOString(new Date("2025-10-16T13:01:09.564Z", "datetime-local")); // "2025-10-16T13:01:09.564"
 *
 * @example
 *   dateToISOString(new Date("not-a-date")); // undefined
 *
 * @param date The JS Date object to convert
 * @param type If the formatted string should include the time and if so, with UTC timezone or as
 *   local time.
 * @returns Returns a full date-only ISO8601 complaint string, which is also parsable by new Date()
 */
export declare const dateToISOString: (date: Date | undefined, type: "date" | "datetime-utc" | "datetime-local") => string | undefined;