Hi yet again...
I know I can use formatter to format different dates for locals.
But how do I change the month/day names in a date chooser

You need to localize the framework resource files.

C:\Program Files\Adobe\Flex Builder
3\sdks\3.1.0\frameworks\projects\framework\bundles \en_US\src\

SharedResources.properties
formatters.properties
controls.properties
validators.properties

Build with this ant file:
C:\Program Files\Adobe\Flex Builder 3\sdks\3.1.0\frameworks\build.xml

Ant target: target name="framework_rb"

Or run this:

bin\compc -locale=en_US
-source-path+=frameworks/projects/framework/bundles/en_US/ src
-include-resource-bundles=collections,containers,controls,core,effec ts,formatter
s,logging,SharedResources,skins,states,styles,vali dators
-output=frameworks/locale/en_US/framework_rb.swc

bin\compc -locale=fr_FR
-source-path+=frameworks/projects/framework/bundles/fr_FR/ src
-include-resource-bundles=collections,containers,controls,core,effec ts,formatter
s,logging,SharedResources,skins,states,styles,vali dators
-output=frameworks/locale/fr_FR/framework_rb.swc

bin\compc -locale=ja_JP
-source-path+=frameworks/projects/framework/bundles/ja_JP/ src
-include-resource-bundles=collections,containers,controls,core,effec ts,formatter
s,logging,SharedResources,skins,states,styles,vali dators
-output=frameworks/locale/ja_JP/framework_rb.swc