Thank you for your question.
Since it started setting a target, Canada has always used 2005 as a base year, and it will continue to do so. Many other countries use this year as a base, but you make a good point: all countries in the world must use the same base year in order to have equivalents between them and for citizens to understand.
I would also like to say that the bill you proposed in 2015 used 2005 as the base year, and a 30% reduction between 2005 and 2030.