The addition of date windows on watches began in the early 20th century. The first wristwatch with a date window is believed to have been introduced by Rolex in 1945 with the launch of the Rolex Datejust. The Datejust featured a small aperture at the 3 o'clock position on the dial, which displayed the date in a magnified window.
Before the introduction of date windows, pocket watches had the ability to display the date on a separate sub-dial, but this feature was not commonly found on early wristwatches. The date window on wristwatches became more prevalent and popular as watchmaking technology advanced and timekeeping functionality improved.
Today, date windows are a standard feature on many wristwatches, providing a convenient and practical way for wearers to keep track of the date along with the time. Some watches also include additional complications, such as day-date displays, which show both the day of the week and the date in separate windows on the dial. These date features have become essential components of modern watch designs, adding both functionality and aesthetic appeal to timepieces.