In what year did Rolex introduce the Datejust?

Rolex introduced the Datejust in 1945.

The original Datejust, reference 4467, was launched to mark Rolex’s 40th anniversary. It combined the brand’s Oyster waterproof case with a self-winding movement and a date display in a window at 3 o’clock. That combination made it an important milestone in the development of practical everyday wristwatches.

The first Datejust was made only in 18-karat yellow gold. It also introduced design features that became strongly associated with the model, including a fluted bezel and the five-row Jubilee bracelet. The date did not initially change instantly at midnight; Rolex later refined the mechanism so the display could make the now-familiar rapid jump.

A common mix-up is confusing the Datejust with the Day-Date. The Datejust shows the calendar date, while the Day-Date, introduced later in 1956, displays both the day of the week and the date. Modern Datejust watches come in several sizes and combinations of steel, two-tone metal and gold, but their defining date-window concept dates back to 1945.