You would only need to put a date
if your residency changed during the year, and it would be the date during the
tax year. So if you went from non-resident to resident in 2017, you would put
the date you became a resident. If you were a non-resident in 2016 and remain a
non-resident in 2017, then no date is needed because your residency didn’t
change.
You can make changes after you
have filed your tax return through the CRA:
https://turbotax.community.intuit.ca/replies/2647992