In Daniel 1, it would appear that Daniel, Hananiah, Mishael, and Azariah were trained for 3 years before first meeting with and being found faultless by Nebuchadnezzar. However, in Daniel 2, Daniel interprets the king's dream in year 2 of his reign, and has his three friends promoted by the king. So the king would have already known them by the time their training was over.
1 Answer
The year in which Nebuchadnezzar came to the throne is his accession year. His year 1 begins at the Babylonian New Year (1 Nisannu) following his accession. His year 2 begins at the next Near Year. So theoretically it is possible that the three-year “training” began during his accession year and finished towards the end of year 2.