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    <p>I suppose since MongoDB ObjectId contain a timestamp, you can sort by 'created date' if you will sort by objectId:</p> <pre><code>items.find.sort( [['_id', -1]] ) // get all items desc by created date. </code></pre> <p>And if you want last 30 created items you can use following query:</p> <pre><code>items.find.sort( [['_id', -1]] ).limit(30) // get last 30 createad items </code></pre> <p>I am actualy not sure,i just suppose that ordering by _id should work as described above. I'll create some tests later.</p> <p><strong>Update:</strong></p> <p>Yes it is so. If you order by _id you will automatically order by _id created date. I've done small test in c#, mb someone interest in it:</p> <pre><code> public class Item { [BsonId] public ObjectId Id { get; set; } public DateTime CreatedDate { get; set; } public int Index { get; set; } } [TestMethod] public void IdSortingTest() { var server = MongoServer.Create("mongodb://localhost:27020"); var database = server.GetDatabase("tesdb"); var collection = database.GetCollection("idSortTest"); collection.RemoveAll(); for (int i = 0; i &lt;= 500; i++) { collection.Insert(new Item() { Id = ObjectId.GenerateNewId(), CreatedDate = DateTime.Now, Index = i }); } var cursor = collection.FindAllAs&lt;Item&gt;(); cursor.SetSortOrder(SortBy.Descending("_id")); var itemsOrderedById = cursor.ToList(); var cursor2 = collection.FindAllAs&lt;Item&gt;(); cursor2.SetSortOrder(SortBy.Descending("CreatedDate")); var itemsOrderedCreatedDate = cursor.ToList(); for (int i = 0; i &lt;= 500; i++) { Assert.AreEqual(itemsOrderedById[i].Index, itemsOrderedCreatedDate[i].Index); } } </code></pre>
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    1. POuses for mongodb ObjectId creation time
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    1. USAndrew Orsich
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    1. COyou mean created time instead of created date, right?
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      1. USKamal Reddy
    2. COI'm pretty sure this is only correct when inserting using one process, bc. Mongo objectids are created using something akin to hilo sequences. More specific: `A BSON ObjectID is a 12-byte value consisting of a 4-byte timestamp (seconds since epoch), a 3-byte machine id, a 2-byte process id, and a 3-byte counter`
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      1. USGeert-Jan
    3. CO@Geert-Jan Because the time stamp is the [most significant part](http://en.wikipedia.org/wiki/Most_significant_bit) of an `ObjectId`, it will sort correctly across inserts from multiple processes (to one second precision, assuming the process clocks are well synchronized). To confirm this, see the [implementation of `getTimeStamp()` uses `.slice(0,8)`](https://github.com/mongodb/mongo/blob/v2.4.1/src/mongo/shell/types.js#L324). This `(0,8)` is selecting the most significant four bytes of the `ObjectId` as the time stamp.
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