/**
 * Return true when intervals `[aStart, aEnd]` and `[bStart, bEnd]` share at least one instant.
 *
 * - Uses `Temporal.Instant.compare` for comparison (same instant semantics).
 * - Adjacent intervals (e.g. `aEnd === bStart`) do NOT overlap — returns `false`.
 * - Returns `false` if either interval is invalid (`start > end`).
 * - Returns `false` on invalid input (wrong type, malformed strings, leap seconds).
 *
 * @param aStart ISO 8601 UTC datetime string for the first interval start
 * @param aEnd ISO 8601 UTC datetime string for the first interval end
 * @param bStart ISO 8601 UTC datetime string for the second interval start
 * @param bEnd ISO 8601 UTC datetime string for the second interval end
 * @returns true if intervals overlap, or false on invalid input
 *
 * @example intervalsOverlapUtc("2024-01-01T00:00:00Z", "2024-06-30T23:59:59Z", "2024-04-01T00:00:00Z", "2024-12-31T23:59:59Z") // true
 * @example intervalsOverlapUtc("2024-01-01T00:00:00Z", "2024-06-30T23:59:59Z", "2024-07-01T00:00:00Z", "2024-12-31T23:59:59Z") // false (adjacent)
 * @example intervalsOverlapUtc("2024-01-01T00:00:00Z", "2024-06-30T23:59:59Z", "2024-07-02T00:00:00Z", "2024-12-31T23:59:59Z") // false (disjoint)
 * @example intervalsOverlapUtc("invalid", "2024-06-30T23:59:59Z", "2024-04-01T00:00:00Z", "2024-12-31T23:59:59Z") // false
 */
export declare function intervalsOverlapUtc(aStart: string, aEnd: string, bStart: string, bEnd: string): boolean;