… or thereabouts, the canonical date is in “the early spring”.
April 11, 1890: Violet Hunter in window seat for the first time. [COPP]
“A chair had been placed close to the central window, with its back turned towards it. In this I was asked to sit, and then Mr. Rucastle, walking up and down on the other side of the room, began to tell me a series of the funniest stories that I have ever listened to. You cannot imagine how comical he was, and I laughed until I was quite weary. Mrs. Rucastle, however, who has evidently no sense of humor, never so much as smiled, but sat with her hands in her lap, and a sad, anxious look upon her face. After an hour or so, Mr. Rucastle suddenly remarked that it was time to commence the duties of the day, and that I might change my dress, and go to little Edward in the nursery.”
A Day by Day Chronology of Sherlock Holmes according to Ziesler and Christ by William S Dorn DWNP, BSI.