The age is calculated at the birthday and the date.
When date of birth and the date that calculates are input, and "calculate the age" button is clicked, the age is displayed.
The age is displayed by the Mannenrei(general age) and kazoedoshi(A born year is assumed to be "One years old", And it grows old by one whenever the New Year's Day (January 1) is received.).
Full years old: It increases at the age of one whenever born time is assumed, and 0 years old it reaches one's birthday.
Kazoedoshi: It increases at the age of one whenever born time is assumed, and one years old the next January 1 is faced.