¡A buenas horas, mangas verdes!

¡A buenas horas, mangas verdes!
 

How would this translate into English?
What would be the equivalent idiom?

@Nivar: Sería conveniente que escribieras una descripción del significado y ejemplos de cómo se usan los dichos sobre los que tienes dudas, para que sea más fácil para otros usuarios el ofrecer una respuesta. :)

I don't think there is an English idiom for this. In English you can say. "Now you've come to help. Well, it's too late."

:idea:Now that I thnk of it there is an idiom:It's too late. The die is cast.

Thanks Poli. I like that one: "It's too late. The die is cast"

How would you translate "literally": The die is cast... (La muerte se ha forjado, ¿perhaps?)

Regarding Angelicas comment, we use this idiom to express dissatisfaction for the sake of something happening to late.

Literally it could be translated as: "In good time, green sleeves" (Good time in a sarcasting tone). Green sleeves because Castillian middleages "police" (La Santa Hermandad) had green sleeves under their leather garments. (It seems that they used to be always late).

"Die", aquí, no es "muerte", sino "dado", el plural es "dice"... algo como "los dados están echados", "la suerte está echada"... :)

A vale, "Alea iacta est", la famosa frase de César pasando el Rubicón.:)