In sonnet XV the turn occurs at the beginning of the ninth line.
Step-by-step explanation:
Sonnet XV is one of Shakespeare’s most famous sonnets within the Fair Youth sonnet sequence. It is one of the most read sonnets among the 154 sonnets written by him. It is a typical Elizabethan sonnet. It has three quatrains and a couplet. It is also categorized as a Shakespearean sonnet for its rhyming scheme.
At the beginning of the ninth line i.e the third quatrain Shakespeare uses the rhetorical device called the ‘volta’. A volta marks a new thought. It is a shift from the previous views expressed in a poem. So the turn occurs at the beginning of the ninth line.