The Rolex collection introduced in 1945 as the first wristwatch with an automatically changing date display was the Datejust.
Rolex introduced the Datejust for its 40th anniversary. Its defining feature was a date aperture at 3 o’clock that changed automatically at midnight. The early mechanism changed the date gradually, while later versions became associated with the instantaneous change familiar today.
The Datejust should not be confused with the Day-Date, which adds a fully spelled-out weekday display. It also differs from the Oyster Perpetual, a broader Rolex family name that does not specifically identify the date-display model.
A magnifying Cyclops lens over the date was added to Datejust models in 1953. That lens became one of the collection’s most recognizable visual features, although not every Datejust configuration has identical materials, bracelets, bezels or movements.