get mongodb records created in a specific month - mongodb

Question

I'm trying to get a specific range of documents, based on when they were created. What I'm trying to do is something like:
/getclaims/2015-01
/getclaims/2015-02
...
that way a user can browse through all records based on the selected month.
In my database I'm not storing a created_at date, but I know mongodb stores this in the objectid.
I found that I can get records like this:
db.claims.find({
$where: function () { return Date.now() - this._id.getTimestamp() < (365 * 24 * 60 * 60 * 1000) }
})
of course that doesn't filter based on a specific month, but only within a certain time limit.
What would be a possible way of limited a query based on a specific month, using the Timestamp from the objectid's?
I'm using mongoose, but it's probably a good idea to start in mongo shell itself.

Answer 1

Based on the function borrowed from the answer to this question - https://stackoverflow.com/a/8753670/131809
function objectIdWithTimestamp(timestamp) {
// Convert date object to hex seconds since Unix epoch
var hexSeconds = Math.floor(timestamp/1000).toString(16);
// Create an ObjectId with that hex timestamp
return ObjectId(hexSeconds + "0000000000000000");
}
Create a start and an end date for the month you're looking for:
var start = objectIdWithTimestamp(new Date(2015, 01, 01));
var end = objectIdWithTimestamp(new Date(2015, 01, 31));
Then, run the query with $gte and $lt:
db.claims.find({_id: {$gte: start, $lt: end}});