/**
 * Check whether an IANA timeZone identifier observes daylight saving time.
 *
 * - Compares UTC offsets at two dates six months apart (January and July).
 * - A zone is considered to have DST if its offset differs between the two dates.
 * - Returns false for invalid or unresolvable timeZone identifiers.
 *
 * @param timeZone timeZone identifier to check
 * @returns boolean indicating whether the timeZone observes DST
 *
 * @example hasDaylightSaving("America/New_York") // true
 * @example hasDaylightSaving("Europe/Berlin")     // true
 * @example hasDaylightSaving("Asia/Tokyo")        // false
 * @example hasDaylightSaving("UTC")               // false
 * @example hasDaylightSaving("Invalid/Zone")      // false
 */
export declare function hasDaylightSaving(timeZone: string): boolean;