it is not known for sure, but most believe that the book was written around 57 a.d. one of the curious verses in the letter is where paul says "see with what large letters i am writing this in my own hand". (chapter 6, verse 11). this is understood to mean that normally paul used a secretary to write down as he spoke his letters. however he wanted the galatians to be sure it was he himself that was the author of the letter they would receive so he wrote a few lines himself. some believe he had poor eyesight and so had to write with "large letters".