/**
 * Return the week number from a UTC datetime string.
 *
 * - By default uses ISO weeks (Monday-based).
 * - Returns null for invalid input.
 *
 * @param value ISO UTC datetime string (e.g., "2024-03-17T14:30:45Z")
 * @param optionsArg optional: weekStartsOn ("monday" | "sunday") for week calculations
 * @returns Week number (1-53) or null on invalid input
 *
 * @example parseWeekFromUtc("2024-03-17T14:30:45Z") // 11
 * @example parseWeekFromUtc("invalid") // null
 */
export declare function parseWeekFromUtc(value: string, optionsArg?: {
    weekStartsOn?: "monday" | "sunday";
}): number | null;