What I mean is that you must stay in Canada for at least 730 days in ANY 5-year period. You should ensure that there is no period of 5 years, beginning on any date, wherein you didn't spend at least 730 days in Canada. So if you land January 1, 2015 and leave December 31, 2016, you'd better return to Canada by December 31, 2019, because if you don't then there will be the five year period between January 2, 2015 and January 1, 2020 where you will only have spent 729 days in Canada. And then if you still haven't returned to Canada on January 2, 2020, there will be the 5 year period between January 3, 2015 and January 2, 2020 where you will only have spent 728 days in Canada. Does that makes sense?
CIC measures to the day, so save all records of entrance/exit from Canada (such as boarding passes) so you can prove that you have maintained PR.
