Here are some possible meanings depending on the context:
* "A year has [something]": This could be followed by a number of things, such as:
* "A year has 365 days": "Un año tiene 365 días."
* "A year has four seasons": "Un año tiene cuatro estaciones."
* "A year has twelve months": "Un año tiene doce meses."
* "A year has [happened]": This could be followed by an event or experience:
* "A year has passed": "Un año ha pasado."
* "A year has gone by": "Un año ha transcurrido."
* "A year has changed a lot": "Un año ha cambiado mucho."
To understand the full meaning, you need to provide the complete sentence or context.