Hi,
Remember... 2 academic years usually means = 4 semesters. It can be completed continuously in 16 months with no break( in summer/winter), or it can be completed in 20 months with 1 break( in summer/winter) or it can also be completed in 24 months with 2 yearly breaks(in summer or winter). It's all in same thing. Depends on different educational institutes. So, as long as you do a 2 academic year/ atleast 4 semesters/ minimum 16 months of actual study in a full time recognized post secondary course in Canada, you will be eligible for a 3 years PGWP.
Similarly 1 academic year means = minimum 2 semesters/ minimum actual 8 months of study, again can be completed in 12 months with 1 break in summer or winter. Some 1 year courses have 3 semesters, with more credit loads/ or having summer co-op term, and usually PGWP for that varies as per course/credit load.
Hope its clear.
***All opinions expressed are purely personal, and pieces of information mentioned are to the best of my knowledge... You should consult other sources too.