On October 7, 2016, the group released their debut single "Taking You", a track from their debut EP, Only the Beginning, which was released on November 25 of the same year. Their second EP, Something Different, was released on April 21, 2017. Its title track was released as the lead single the same day. They released their third EP, Why Do n't We Just, on June 2, 2017. They finished their "Something Different" tour around the United States. Another single, "These Girls" was released on August 29, 2017.

Based on this passage, when did why dont we release their first song? Let's think fast. Stream of consciousness:
To answer this question, we should know that: On October 7, 2016, the group released their debut single "Taking You", a track from their debut EP, Only the Beginning, which was released on November 25 of the same year. So the final answer is October 7 , 2016.