mongodb Date strings and other issues
Is very bad for lots of registers... if you need accessing a file, need typing db.collection.find({"hours.hour":"05", "hours.file.name":"name"}). And you hours arrays will grow  very fast...

You can having a struct like this,

{ 
    _id   : {date:"2014-02-13",hour: "00"}, files: [
                     {name:"something.csv", date_added : ISODate("2014-04-04T08:59:34.268Z")}, 
                     {...},
                     {...}]
 }


Having a documents with a array having little data and where you find very fast...