The Rolex watch introduced in 1971 with a 24-hour hand for distinguishing day from night is the Explorer II.
Rolex designed the Explorer II for people working in environments where natural light could disappear for long periods, including explorers and cave researchers. Its additional hand makes one complete revolution every 24 hours, pointing to a fixed 24-hour scale on the bezel. This lets the wearer tell whether it is daytime or nighttime when ordinary visual cues are unavailable.
The first Explorer II was reference 1655. Early examples had an orange 24-hour hand and a distinctive dial layout, features that later made vintage versions especially collectible. The model has remained part of Rolex’s professional sports-watch range.
The Explorer II is often confused with the GMT-Master II because both can show a second time indication. The GMT-Master II uses a rotating bezel for tracking another time zone, while the Explorer II’s fixed 24-hour bezel was originally intended primarily as a day-and-night indicator.