Definitely the first information is accurate. 6 months has become a bit conservative over the years, as new and improved testing technologies are implemented. The truth is the standard ELISA which has been in use for years, has been found reliable when taken at 3 months.
Study has and currently continues to determine that most infected patients seroconvert in 4-6 weeks after initial infection. CDC used to have a 6 month window. They recently changed that to 3 months. They still keep 6 months for extremely risky exposures, where a person known to have HIV was involved. But for most cases, 3 months is sufficient.
If your doctor ever tells you you need a year or 2 to be sure, I'd advise you to quickly see another doctor who is knowledgeable AND updated on the subject.