Unfortunately, there is no set date. The state government intended to use 2017 to establish rules and regulations and begin granting licenses in early 2018, but some think the process will take longer than expected. This would likely push the recreational market’s open to 2019. The state government has to go through a lengthy rule-making process before licenses can be granted to producers and retailers. As of now, no one is positive how long that process will take.
Here is an article explaining potential delays on recreational cannabis in more detail:
Hope that helps!