/**
 * Convert a UTC datetime string to a plain date string in the format "YYYY-MM-DD".
 *
 * - Converts to specified timezone before extracting date.
 * - Defaults to UTC if no timezone specified.
 * - Returns "" for invalid input.
 *
 * @param value UTC datetime string (e.g., "2024-02-29T00:00:00Z")
 * @param options optional: timeZone (IANA)
 * @returns plain date string in "YYYY-MM-DD" format or "" on invalid input
 *
 * @example convertUtcToPlainDate("2024-02-29T00:00:00Z") // "2024-02-29"
 * @example convertUtcToPlainDate("2024-02-29T00:00:00Z", { timeZone: "America/New_York" }) // "2024-02-28"
 * @example convertUtcToPlainDate("invalid") // ""
 */
export declare function convertUtcToPlainDate(value: string, options?: {
    timeZone?: string;
}): string;