When did Mary Magdalene discover that the stone was taken away from the tomb?
Mary Magdalene discovered the stone had been taken away on the first day of the week, early in the morning while it was still dark, before daylight, when she came to the sepulcher. This occurred on resurrection morning, according to John's Gospel chapter 20.
Les explains that John's Gospel chapter 20 opens on resurrection morning. As the custom was, they anointed the body of the deceased with herbs and spices even a day or so after burial. They were not buried underground as we think of it, but were placed in a cave. Mary Magdalene, in verse 1, came on the first day of the week early, no doubt even before daylight, and when it was dark she came to the sepulcher and discovered the stone taken away. Peter and John hear it from Mary, run full speed for the sepulcher, John gets there first but is more timid, and Peter bursts right in; then John joins him in the sepulcher.
The first day of the week cometh Mary Magdalene early, when it was yet dark, unto the sepulchre, and seeth the stone taken away from the sepulchre.