In the ESV, this verse is: "Now on the first day of the week Mary Magdalene came to the tomb early, while it was still dark, and saw that the stone had been taken away from the tomb."
I realized that the description "while it was still dark," while providing a veritable detail of the account, could also be understood metaphorically. Its being "still dark" could also refer either to the gloom of Mary's sadness after Jesus' death or to her ignorance of His resurrection.