/**
 * Return true when two Unix intervals are exactly adjacent — one's end equals the other's
 * start minus 1 (no gap, no overlap).
 *
 * - Compares numeric Unix epoch values directly.
 * - Returns `true` when `aEnd + 1 === bStart` or `bEnd + 1 === aStart`.
 * - Returns `false` when intervals overlap, are disjoint with a gap, or are invalid.
 * - Returns `false` on invalid input (non-numeric types, non-finite values).
 *
 * @param aStart Unix epoch value (seconds or milliseconds) — first interval start
 * @param aEnd Unix epoch value (seconds or milliseconds) — first interval end
 * @param bStart Unix epoch value (seconds or milliseconds) — second interval start
 * @param bEnd Unix epoch value (seconds or milliseconds) — second interval end
 * @returns true if intervals are exactly adjacent, or false on invalid input
 *
 * @example intervalAbutsUnix(0, 1500000000, 1500000001, 1700000000) // true
 * @example intervalAbutsUnix(1500000001, 1700000000, 0, 1500000000) // true
 * @example intervalAbutsUnix(0, 1500000000, 1500000002, 1700000000) // false (gap)
 * @example intervalAbutsUnix(0, 1500000001, 1500000000, 1700000000) // false (overlap)
 * @example intervalAbutsUnix(NaN, 1500000000, 1500000001, 1700000000) // false
 */
export declare function intervalAbutsUnix(aStart: number | string, aEnd: number | string, bStart: number | string, bEnd: number | string): boolean;