Nominal age, born 1 year, Spring Festival every year 1 year. According to the lunar calendar.
The exact age refers to the number of days from the date of birth to the date of calculation. It reflects people's real life time more accurately than one-year-old age, but it is rarely used for demographic statistics because of its complicated statistical summary. In real life, except for babies under 1 year, especially newborns under 1 month, people usually don't calculate the exact age by day.