The Quinceañera is the celebration of the passage from girlhood to womanhood. It is held when a girl turns

15 years old.

To find the answer to this question, one can either have prior knowledge about the tradition of Quinceañera or conduct a quick internet search. The celebration of Quinceañera is a cultural tradition mainly observed in Latin American countries, particularly in Mexico, Central, and South America. It marks a significant milestone in a young girl's life, symbolizing her transition from childhood to adulthood.

The word "Quinceañera" itself is derived from the Spanish words "quince" (meaning fifteen) and "años" (meaning years). Hence, it is commonly celebrated when a girl turns fifteen years old. However, variations of this celebration can be found in different cultures, with different names and ages.

Overall, understanding the significance and timing of a Quinceañera requires familiarity with cultural traditions or conducting research to gather accurate information.