As for how long it takes to complete undergraduate credits, it depends on many factors, such as: how many courses to take each semester, whether the selected courses pass the exam, whether to go to summer school, which university to attend, what major to study, and so on. If you take more than six courses each semester and take classes in summer, you can graduate in three years as big as McGill, UBC and these famous universities. On the other hand, if you only take three courses each semester and don't attend classes in summer, an ordinary undergraduate university may not graduate in four years.
However, there are some famous universities in Canada, which take longer to complete undergraduate credits than other ordinary universities. For the convenience of expression, we call these two types of universities "four-year system" and "three-year system" respectively.
Generally speaking, undergraduate graduates of such "four-year" universities can directly apply for graduate students with their bachelor's degrees. And those undergraduate graduates from "three-year" universities also have bachelor's degrees. They have to take another "honorary bachelor's degree" to apply for graduate students, and generally have to study for one more year to get an honorary bachelor's degree. In this way, the "three-year system" has become a "four-year system".