/**
 * 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;
/**
 *
 * @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()
 *
 * @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
 */
export declare const dateToISOString: (date: Date | undefined, type: "date" | "datetime-utc" | "datetime-local") => string | undefined;