Couldn't translate Date to spanish with Locale("es_ES")

I'm trying to do a simple date format, it does work great, it's very easy, but the problem is the language. I used the locale "es_ES" to get "Miércoles" instead of "Wednesday" and sorts like that but i failed.

Here's my code:

SimpleDateFormat formato = 
    new SimpleDateFormat("EEEE d 'de' MMMM 'de' yyyy", new Locale("es_ES"));
String fecha = formato.format(new Date());

The EXPECTED value of the fecha string is:

Miércoles 4 de Abril de 2012

but i'm still getting:

Wednesday 4 de April de 2012

What am I doing wrong?

"es_ES" is a language + country. You must specify each part separately.

The constructors for Locale are:

• Locale(String language)
  Construct a locale from a language code.
• Locale(String language, String country)
  Construct a locale from language, country.
• Locale(String language, String country, String variant)
  Construct a locale from language, country, variant.

You want new Locale("es", "ES"); to get the Locale that goes with es_ES.

However, it would be better to use Locale.forLanguageTag("es-ES"), using the well-formed IETF BCP 47 language tag es-ES (with - instead of _), since that method can return a cached Locale, instead of always creating a new one.