JSON Date field

Add date via json into DB:
method: node.save (update node)

When I try to add a date in the database is restricted to null.
The Date field allowe Year,Month,Day,Hour,Minute

I get no error :/ whats wrong ?! BUG ?!

thx

POST:
{"nid":"247","title":"H222ello World6asdasd","field_date_test":[[{"year":"2011"},{"month":"5"},{"day":"10"},{"hour":"20"},{"minute":"22"},{"timezone_db":"Europe/Berlin"},{"date_type":"date"}]]}

RESPONSE:
{ "#error": false, "#data": "247" }