Here is what Italy has to say: Italy deems you resident for tax purposes if you've stayed there at least 183 days in the past tax year.
You can click here to see if you've become a Canadian resident for tax purposes.
Canada generally goes by a date of December 31, so if you are resident here December 31, 2017, you would file taxes here for the 2017 tax year (by the deadline of April 30, 2018).
Note that you might need to be careful about health insurance. For example, in Canada, if you haven't become a resident, you won't qualify for the publicly-funded plans, but if you've ceased to be an Italian resident, you may have no benefits available to you from there. You'd need to secure insurance from a private insurer. (Such policies can be acquired by foreigners living in Canada temporarily, but typically aren't valid outside Canada. Source: am an insurance broker in Canada.)