How do I extract the created date out of a Mongo ObjectID

I'm using the Mongo shell to query my Mongo db. I want to use the timestamp contained in the ObjectID as part of my query and also as a column to extract into output. I have setup Mongo to create ObjectIDs on its own.

My problem is I can not find out how to work with the ObjectID to extract its timestamp.

Here are the queries I am trying to get working. The 'createdDate' field is a placeholder; not sure what the correct field is:

//Find everything created since 1/1/2011
db.myCollection.find({date: {$gt: new Date(2011,1,1)}});

//Find everything and return their createdDates
db.myCollection.find({},{createdDate:1});