Okay, thank you I've tried this
<f:format.date>{item.node.properties.dateBlogArticle -> f:format.date(forceLocale: 'de_DE', cldrFormat: 'MMM')}</f:format.date>
and I get:
"Mai" could not be parsed by \DateTime constructor. (20150609135105845de2)
he recognizes that it "Mai" have to be called, but he could not parse :-(