thumb|250px|right|NIST-F1, source of the official time of the United States
thumb|250px|right|NIST-F1, source of the official time of the United States
NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and served as the United States' primary time and frequency standard. The clock took fewer than four years to test and build, and was developed by Steve Jefferts and Dawn Meekhof of the Time and Frequency Division of NIST's Physical Measurement Laboratory.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).