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

Question

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 h

Answer 1

getTimestamp()

The function you need is this one, it's included for you already in the shell:

ObjectId.prototype.getTimestamp = function() {
    return new Date(parseInt(this.toString().slice(0,8), 16)*1000);
}

References

Check out this section from the docs:

• Extract insertion times from _id rather than having a separate timestamp field

This unit test also demostrates the same:

• mongo / jstests / objid6.js

Example using the Mongo shell:

> db.col.insert( { name: "Foo" } );
> var doc = db.col.findOne( { name: "Foo" } );
> var timestamp = doc._id.getTimestamp();

> print(timestamp);
Wed Sep 07 2011 18:37:37 GMT+1000 (AUS Eastern Standard Time)

> printjson(timestamp);
ISODate("2011-09-07T08:37:37Z")