Pippi was born from February 29, 2004 to 2020. How old is he?

Real age 16 years old, nominal age 17 years old.

1, one year old, Pippi was zero when he was born on February 29th, 2004, and he will be one year older every Gregorian birthday. He was one year old on February 29th, 2005, so the monkey born in 2004 will be 16 years old in 2020.

2, nominal age, Pippi is one year old when he was born, and one year old every Spring Festival. Therefore, monkeys born in 2004 will be 17 years old in 2020.

3. Therefore, Pippi was born from February 29th, 2004 to 2020. His real age is 16, and his nominal age is 17.