The transition between chapters 1 and 2 of John is extremely awkward. Chapter 1 ends with Jesus speaking to Nathanael, a newly met disciple. Chapter 2 begins, "And the third day a wedding took place in Cana..."
The third day of what!?!
John gives no clue what the third day means. The third day of the week? The third day of the month? The third day of his brand new job? He doesn't say. I don't think he cares, because for him the third day had a deeper significance.
Of course, Jesus was resurrected on the third day after his death. In the context of John chapter 2, the third day also signifies resurrection! The next several verses talk about Jesus changing the water into wine, a sign (verse 11) for changing death into life, which is resurrection.
John's gospel is a gospel all about life, and from the first verse of chapter 2, he sets forth this principle of resurrection.