ABC:Galatians 1

Verse 18
Wikipedia claims the Bible is wrong about the following passage, and makes the following comments (italicized):

Acts 9; 11; 15; 18:22; 21 vs. Galatians 1:18; 2:1. Acts 18:22 And when he had landed at Caesarea, and gone up, and saluted the church, he went down to Antioch. Galatians 1:18 Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days. Galatians 2:1 ¶ Then fourteen years after I went up again to Jerusalem with Barnabas, and took Titus with me also.

Wikipedia does not specify why this is considered a contradiction. It is possible that it involves what was done in Jerusalem, and to what degree Paul was known in the city, as addressed by John Oakes of Evidence for Christianity and Chris Blomberg of Biblical Training. However, without clarification as to why a contradiction is assumed to exist, supposition would be futile.