@attilakinali Here is the document:
whitehouse.gov/wp-content/uplo

and in particular, the goals:
1. Traceability to Coordinated Universal Time (UTC);
2. Accuracy sufficient to support precision navigation and science;
3. Resilience to loss of contact with Earth; and
4. Scalability to space environments beyond the Earth-Moon system

It is still linked to UTC, as far as I can tell (bullet 1).