If Jesus arose early Sunday morning, how could He appear to His disciples in the locked room (John 20:19) on the evening of the first day of the week? Wouldn't this be before Sunday morning?
The first day of the week in Jesus' day was Sunday (as it still is today for many). The Gospels report Jesus rose from the tomb before dawn on the first day of the week, and John also reports He appeared to the disciples on the evening of that same day. Notice John's entire narrative about that day:
John 20:1 Now on the first day of the week Mary Magdalene came early to the tomb, while it was still dark, and saw the stone already taken away from the tomb.
John 20:2 So she ran and came to Simon Peter and to the other disciple whom Jesus loved, and said to them, “They have taken away the Lord out of the tomb, and we do not know where they have laid Him.”
John 20:3 So Peter and the other disciple went forth, and they were going to the tomb.
John 20:4 The two were running together; and the other disciple ran ahead faster than Peter and came to the tomb first;
John 20:5 and stooping and looking in, he saw the linen wrappings lying there; but he did not go in.
John 20:6 And so Simon Peter also came, following him, and entered the tomb; and he saw the linen wrappings lying there,
John 20:7 and the face-cloth which had been on His head, not lying with the linen wrappings, but rolled up in a place by itself.
John 20:8 So the other disciple who had first come to the tomb then also entered, and he saw and believed.
John 20:9 For as yet they did not understand the Scripture, that He must rise again from the dead.
John 20:10 So the disciples went away again to their own homes.
John 20:11 But Mary was standing outside the tomb weeping; and so, as she wept, she stooped and looked into the tomb;
John 20:12 and she saw two angels in white sitting, one at the head and one at the feet, where the body of Jesus had been lying.
John 20:13 And they said to her, “Woman, why are you weeping?” She said to them, “Because they have taken away my Lord, and I do not know where they have laid Him.”
John 20:14 When she had said this, she turned around and saw Jesus standing there, and did not know that it was Jesus.
John 20:15 Jesus said to her, “Woman, why are you weeping? Whom are you seeking?” Supposing Him to be the gardener, she said to Him, “Sir, if you have carried Him away, tell me where you have laid Him, and I will take Him away.”
John 20:16 Jesus said to her, “Mary!” She turned and said to Him in Hebrew, “Rabboni!” (which means, Teacher).
John 20:17 Jesus said to her, “Stop clinging to Me, for I have not yet ascended to the Father; but go to My brethren and say to them, ‘I ascend to My Father and your Father, and My God and your God.’”
John 20:18 Mary Magdalene came, announcing to the disciples, “I have seen the Lord,” and thatHe had said these things to her.
John 20:19 So when it was evening on that day, the first day of the week, and when the doors were shut where the disciples were, for fear of the Jews, Jesus came and stood in their midst and said to them, “Peace be with you.”
Notice in v.1 John says Jesus rose on the first day of the week (i.e., Sunday). Then later in v.19 John says "when it was evening on that day, the first day of the week," speaking of the same day as mentioned in v.1. So Jesus arose before sunrise on Sunday and later appeared to the disciples on that same day.