Using DateTime under db4o with native SODA queries?

Under db4o, I'm attempting to con开发者_JAVA百科strain by a "new DateTime(2010,10,14)" but it doesn't seem to work - any opinions on how to fix this?

Got it:

var query2 = db4o.db.Query();
query2.Constrain(typeof(TradingDay));
query2.Descend("_date").Constrain(new DateTime(2010,10,14));
IObjectSet result2 = query2.Execute();