Sun/moon dial on a watch

Antiquorum-Lexico.pdf, an “Illustrated Horological Glossary”, on page 134 (pdf page 13) apparently refers to that dial like that as a “Day/night” dial.

Astronomically-related terms elsewhere in the glossary's dial section include Astrolabe, p. 133; Moon phase and Planetarium, p. 136; Star chart and Sunrise, sunset, p. 137.

From Wikipedia : An astronomical clock is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.

So, I gess, you could call that an astronomical wristwatch or dial, as they do in the article.