I think the colleges you describe are referring to academic years, not necessarily calendar years. Most four-year colleges expect degree candidates to earn at least half their credits there. That is why they discourage students who will have studied for more than two years at another institution from applying. If, for instance, you had been studying part-time somewhere while working for several years, and only had the equivalent of 1-2 years’ credits, you would probably still be eligible. Do not set your sights on transferring to the most selective institutions: that is a guaranteed recipe for disappointment. If you have no chance of getting into Harvard or Stanford today, you are unlikely to have a better chance in two years. The UC system only accepts junior transfers. Period. They are fairly kind toward graduates from California community colleges, but you need a good GPA and to pay attention to the requirements.