According to Galatians 2, Paul went up to Jerusalem for a second time fourteen years after his conversion (1:18; 2:1; Acts 22:17). Some scholars wonder if Paul went up to Jerusalem fourteen years after his first visit with Peter, but I am wary of this idea. I base my understanding on the fact that Paul’s argument in Galatians appears to be that he had no time to learn his Gospel from any man, especially from the Apostles at Jerusalem. Paul is giving an account of himself from the very moment of his new birth which occurred on his way to Damascus when Jesus appeared to him for the first time. It was three years after his new birth that he came to Jerusalem, where he spent less than three weeks with the Apostles, and fourteen years after his new birth that he returned to Jerusalem.
After leaving the Apostles at Jerusalem cir. the spring of 38 CE, Paul had been evangelizing Syria, Cilicia and Galatia. The Gospel which Paul preached, although the same in essence with that of the Jerusalem Apostles, differed in some key responsibilities, but Paul insisted that his Gospel came from Jesus despite those differences. Paul’s Gospel was neither thought up by man, nor did it come to him through any human agency (Galatians 1:1). Fourteen years after his heavenly vision, Paul returned to Jerusalem by revelation (cp. Acts 11:28-30; 12:25). This visit was the very same visit mentioned in Acts 15, and it took place cir. spring of 49 CE. The men from James, whom Paul referred to as false brethren, had tried to insist on circumcision for the gentile believer, Titus, who accompanied Paul to Jerusalem. However, Paul adamantly refused their demands (Galatians 2:4-5).
Note that the initial purpose of Paul’s second visit to Jerusalem was to go to Jerusalem with the gift for the poor (Galatians 2:1-2; cp. Acts 11:28-30). Paul and Barnabas may have been originally appointed for this task years earlier when the prediction of the famine was made by Agabus, the prophet (cir. 41-44 CE), or it may have been decided by the church at Antioch that both Paul and Barnabas take their offering to the poor and at the same time take the issue of circumcision to the Apostles as well. This journey to Jerusalem took place about eleven years after Paul’s first meeting with Peter (Acts 9:27; Galatians 1:18; Galatians 2:1)
Although he had returned to Jerusalem with a gift to the poor, ultimately Paul’s visit was turned into an official visit to explain his Gospel to the leaders at Jerusalem (Acts 15:1-3). Paul first visited, privately, with the leaders of the Jerusalem church (Galatians 2:2), and afterward he reported to Jerusalem’s church body (Acts 15:5).
One might ask: if Paul did not need human authorization to preach the gospel, why did he present his Gospel to the leaders in Jerusalem at all (Galatians 2:1-2)? Paul needed the support of the Jerusalem leadership to prevent division among the brethren. He was seeking to avert a real church split between Jewish and gentile Christians. He presented his version of the Gospel to the leadership, privately, in case he had to explain anything about his Gospel. Such a thing is done better without a lot of others around preventing progress being made in a discussion. Paul was concerned about failing both in keeping Church unity and in preventing a victory by the agitators in successfully attacking and undoing all Paul had been doing among the gentiles (Galatians 2:2c). If Paul refused to meet with the Jewish leaders at Jerusalem, the agitators (the men from James) could argue that Paul was uncooperative and a rebel in the community.
The proof that the Jerusalem authorities (i.e. the Apostles) agreed with Paul was the fact that Titus, a Greek was not compelled to be circumcised (Galatians 2:3). Although the false brethren sought to compel Titus to be circumcised (Acts 15:1, 5), the church leaders at Jerusalem didn’t agree. This is significant in that, if the Jerusalem church leaders (which included the Apostles) didn’t require gentile circumcision in order to be saved, then Paul was misrepresented by the agitators at Galatia, and the Council’s decision showed the men from James were clearly wrong and overstepped their authority in what they did, while bringing news of the state of the poor at Jerusalem.