Thanks for the valuable information. I will follow the same idea but much tougher implementation ( 4.5 hr drive from Stanstead Quebec to New Haven Connecticut Mon/Thu morning, went back Tue/Fri night). Hopefully, I can get 7 fully physical presence day credits.
For everyone's reference, below is the official information:
https://eservices.cic.gc.ca/rescalc/redir.do;jsessionid=6E17FDB75632F036720991F15C701736?redir=faq
A3
When calculating an absence, the day you leave Canada and the day you return is NOT considered an absence. Both are counted as days of physical presence because you were physically in Canada for a part of the day of departure or arrival. For example, an absence between July 1, 2013 and July 15, 2013 equals 13 days of absence. As another example, if you leave Canada on July 1, 2013 and return on July 2, 2013, this equals 0 days of absence. You must still declare this as an absence. Think of it as counting only the full days outside of Canada.
I will likely need to do this life-wasting commute for 15 months since I only live in Canada as a PR for 11 months (2016 Sep to 2017 Aug). I have two years (2014 Sep to 2016 Sep) of pre-PR international student residence that can be converted into one year. I, unfortunately, didn't do commute back to Canada from 2017 Aug to 2018 Aug. I worked very hard on EB1A green card petition hoping to get US GC soon but just so dam disappointed about the recent retrogression for EB1-China green card applicants.