mongo db date saved as string, convert to ISO Date using RoboMongo or Python's PyMongo

Question

First of all, I am not a mongo db expert, so I might have some newbie mistakes. I have a mongodb database that was created with pymongo a while ago, from parsing a json. A sample piece of code is this:

data = {parsed_json['location']['city']:
                 'local_time': parsed_json['current_observation']['local_time_rfc822'],
                 'full_name': parsed_json['current_observation']
                                         ['observation_location']['full'],
                 'latitude': float(parsed_json['current_observation']
                                              ['observation_location']
                                              ['latitude']),
                 'longitude': float(parsed_json['current_observation']
                                               ['observation_location']
                                               ['longitude']),
                 'elevation_ft': float(parsed_json['current_observation']
                                                  ['observation_location']
                                                  ['elevation'].split(' ')[0])
                 }}
        collection = db[state_to_insert]
        collection.insert_one(data)
        print 'Inserted data successfully'

The output in the db looks like the one below, however, one of the fields "local_time" is saved in the wrong format (string instead of date).

{
    "_id" : ObjectId("5adb54ff59aea50aec2856bf"),
    "Ithaca" : {
        "weather" : "Clear",
        "full_name" : "Ithaca, New York",
        "windchill_f" : 47.0,
        "solarradiation" : 786,
        "heat_index" : "NA",
        "latitude" : 44.7,
        "wind_mph" : 0.0,
        "dewpoint" : 23,
        "precip_today_in" : 0.0,
        "temp_f" : 47.0,
        "elevation_ft" : 174.0,
        "pressure_trend" : "0",
        "visibility_mi" : 10.0,
        "wind_string" : "Calm",
        "pressure_in" : 30.34,
        "wind_dir" : "NNW",
        "wind_degrees" : 336.0,
        "relative_humidity_perc" : 0.38,
        "uv" : 3.7,
        "longitude" : -73.47,
        "local_time" : "Sat, 21 Apr 2018 11:13:03 -0400",
        "wind_gust_mph" : 0.0,
        "feels_like" : 47
    }
}

My db is running on a local machine, in a db that has one collection called "NY":

To fix the data type, so I can query the database properly by date, in robomongo, I run the following code:

db.NY.find().forEach(function(element){
  element.local_time = new Date(element.local_time);
  db.NY.save(element);
})

Which produces the following output:

{
    "_id" : ObjectId("5adb54ff59aea50aec2856bf"),
    "Ithaca" : {
        "weather" : "Clear",
        "full_name" : "Ithaca, New York",
        "windchill_f" : 47.0,
        "solarradiation" : 786,
        "heat_index" : "NA",
        "latitude" : 44.7,
        "wind_mph" : 0.0,
        "dewpoint" : 23,
        "precip_today_in" : 0.0,
        "temp_f" : 47.0,
        "elevation_ft" : 174.0,
        "pressure_trend" : "0",
        "visibility_mi" : 10.0,
        "wind_string" : "Calm",
        "pressure_in" : 30.34,
        "wind_dir" : "NNW",
        "wind_degrees" : 336.0,
        "relative_humidity_perc" : 0.38,
        "uv" : 3.7,
        "longitude" : -73.47,
        "local_time" : "Sat, 21 Apr 2018 11:13:03 -0400",
        "wind_gust_mph" : 0.0,
        "feels_like" : 47
    },
    "local_time" : ISODate("1970-01-01T00:00:00.000Z")
}

So, the function seems to work in robomongo, however, the behavior is not the expected one since:

"local_time" : "Sat, 21 Apr 2018 11:13:03 -0400"

Is transformed into:

"local_time" : ISODate("1970-01-01T00:00:00.000Z")

Furthermore, all the other dates in the record are the same. What's the problem here? Anybody can point out where the error is?

Answer 1

There is no element.local_time in your forEach. element here is the document, so it should be:

db.NY.find().forEach(function(element){
  element.local_time = new Date(element.Ithaca.local_time);
  db.NY.save(element);
})