Because usually square dances are danced to music, and a piece of music is usually just 2 minutes to 3 minutes long. So it's 3 minutes.
Square dance is the most huge system in the art of dance, named for the gathering in the square, integrating self-indulgence and performances, taking group dance as the main form of performance, and taking fitness as the main purpose. Including Jiamusi dance, dam dance, sailor dance and so on. Square dance is the residents of the spontaneous fitness for the purpose of square, dam and other open space on the rhythmic dance, usually accompanied by high decibel, rhythmic music accompaniment.