Tiene un año de edad.
You say "one year old" when referring to a person's age. Saying "one years old" is grammatically incorrect.
A dog is one year old. Although we may say it has lived the equivalent of say 6 human years, it has been alive for one year, so we say its one year old.
Viejo Feliz
You are one year old. = Tu as un an. -OR- Vous avez un an. I am one year old. = J'ai un an.
You would say "a" one year old child, because it is based on the *sound* rather than the letter. One has a W (consonant) sound to start it, so it uses an "a" rather than an "an."
Tiene catorce años.
un año (with a tilde, the little wave, on the 'n')
Tengo una hija de viente nueve anos.
De una vieja señora a otra
i have age, if you want to say how old u are say 'soy (number in spanish) anos'
The expression to say how old you are or a material object is in Spanish is "tener ____ años".If you literally want to translate "years old" into Spanish, this would be "años de vejez", but this is nonsense to any Spanish speaker.
The word "year" is "año" in Spanish.