For the PR Residency Obligation, you can count the day you entered Canada and all days you remained in Canada after entering Canada, and the day you left Canada.
There are 365 days in a year (leap days do not count, so February 29, 2012 does not count).
Count the number of days you have been in Canada each year for the last five years. Add them up. If that number adds up to 730 or more, you have met the PR Residency Obligation. If not, you haven't.
If that seems difficult, list every month of the year for all five years. Count the number of days you were in Canada during each of those months. Add them up. More than 730, you are OK. Less than 730, problems.
If that is difficult, get a copy of a full year calendar for each year (easy to print off the internet), and start circling all the days you were in Canada. Count how many days you circle. Again, you can circle (count) each day you arrived in Canada, all the days you stayed after arriving, and the day you left.