Contradiction with Matthew 28:1
This verse mentions Mary Magdalene and the other Mary visiting the tomb at dawn, contradicting the "early, when it was yet dark" timing in John 20:1.
Matthew 28:1: In the end of the sabbath, as it began to dawn toward the first [day] of the week, came Mary Magdalene and the other Mary to see the sepulchre.
Contradiction with Mark 16:2
This verse states that Mary Magdalene and others went to the tomb "very early in the morning" when the sun had risen, differing from John's account of it being dark.
Mark 16:2: And very early in the morning the first [day] of the week, they came unto the sepulchre at the rising of the sun.
Contradiction with Luke 24:1
This verse describes the visit to the tomb happening "very early in the morning" with more than just Mary Magdalene, contrasting with John 20:1's mention of the visit occurring while it was still dark.
Luke 24:1: Now upon the first [day] of the week, very early in the morning, they came unto the sepulchre, bringing the spices which they had prepared, and certain [others] with them.