/**
 * Return the latest (maximum) of the given PlainDateTime values.
 *
 * - Returns null if the array is empty or contains no valid datetimes.
 * - Validation is performed on each item in the array.
 *
 * @param dateTimes Array of ISO PlainDateTime strings (e.g. "2024-03-10T12:00:00")
 * @returns The latest datetime string, or null on invalid input
 *
 * @example maxDateTime(["2024-03-10T12:00:00", "2024-03-15T12:00:00", "2024-03-12T12:00:00"]) // "2024-03-15T12:00:00"
 * @example maxDateTime([]) // null
 */
export declare function maxDateTime(dateTimes: string[]): string | null;