Ashton Kutcher and Mila Kunis welcomed their second child, a son named Dimitri Portwood Kutcher, in November 2016. This date is well-documented, marking a significant moment in their family life, as they had previously welcomed their first child, a daughter named Wyatt, in 2014. The timeline of their children’s births places Dimitri's arrival firmly in 2016, making it the accurate answer to the question.