finding the documents containing a value closest to the paramater passed in mongodb+node.js

I have a mongodb collection called lights and a document in this collection looks like,

{
    "_id": "50eea4a53004cc6233d12b02",
    "Physicalentity": "Light",
    "Sensor": "Tinkerforge",
    "Unit": "Lux",
    "value": "47.2",
    "time": "12:23:17",
    "date": "10.01.2013"
  },

I would like to retrive a document based on the time, hence to accomplish this, I wrote the following:

    app.get('/lights/:time', function(req, res) {
    var time = req.params.time;
console.log('Retrieving value: ' + time);
db.collection('lightsensor', function(err, collection) {
        collection.findOne({'time':new BSON.ObjectID(time)}, function(err, item) {
            res.send(item);
        });
    }); 
    });

But when I enter the URL http://localhost:3000/lights/12:23:17

I get Error: Argument passed in must be a single String of 12 bytes or a string of 24 hex characters

Where exactly is the problem?

And is it possible to enter a time and allow mongodb, to find the document which has the closest time specified in the URL.

For instance, I enter http://localhost:3000/lights/12:23:20

Which is not in my collection but a document with time 12:23:17 exists.

How can I tell mongodb to find the documents containing a value closest to the paramater passed.