/**
 * @file Spec clause 21.x host hook — wallclock reader. Implements
 *   `SystemUTCEpochNanoseconds()`, the spec's nanosecond- resolution wallclock
 *   read. Hosts may use any source they like provided the result is
 *   non-decreasing across calls. On Node we combine `Date.now()` (millisecond
 *   wallclock) with `process.hrtime.bigint()` (sub-millisecond monotonic
 *   counter) anchored at module load to deliver real nanosecond resolution.
 *   Fallback path (non-Node hosts without `process.hrtime.bigint`): we multiply
 *   `Date.now()` by 1_000_000n to fill the field with zeros. This trades
 *   sub-millisecond precision for portability and is the same compromise the
 *   polyfill makes for browser hosts. Spec:
 *   https://tc39.es/proposal-temporal/#sec-temporal-systemutcepochnanoseconds.
 */
/**
 * Returns the current UTC time as nanoseconds since 1970-01-01T00:00:00Z.
 *
 * Resolution is nanosecond on Node (via `process.hrtime.bigint` anchored at
 * module load), millisecond elsewhere.
 */
export declare function systemUTCEpochNanoseconds(): bigint;
