MGO time.Time with Location is automatically converted to UTC?

[al...@deefuse.com]

Hi,

This is more of a confirmation rather than a question: a time.Time with a time.Location attached to it, when inserted into MongoDB gets "automagically" converted to the UTC time?

For example:

type Test struct {    
    Date time.Time    
}


func main() {
    var err error    
   
    loc, err := time.LoadLocation("Europe/Bucharest")    
    if err != nil {    
        log.Fatal(err)    
    }    
    lay := "2006 Jan _2 15:04:05"    
    val := "2015 Nov 26 19:00:00"


    t1, err := time.Parse(lay, val)    
    if err != nil {    
        log.Fatal(err)    
    }    
    fmt.Printf("t1: %+v\n", t1)    
    fmt.Printf("u2: %+v\n", t1.UTC())    
    fmt.Printf("s1: %+v\n", t1.Unix())    
    fmt.Println("")    
   
    t2, err := time.ParseInLocation(lay, val, loc)    
    if err != nil {    
        log.Fatal(err)
    }
    fmt.Printf("t2: %+v\n", t2)
    fmt.Printf("u2: %+v\n", t2.UTC())
    fmt.Printf("s2: %+v\n", t2.Unix())
    fmt.Println("")


    s, _ := mgo.Dial("...")
    coll := s.DB("...").C("test")


    err = coll.Insert(&Test{
        Date: t1,
    })


    err = coll.Insert(&Test{
        Date: t2,
    })


    var res []Test
    err = coll.Find(bson.M{}).All(&res)
    fmt.Printf("%+v\n", res)


}

Go output:

t1: 2015-11-26 19:00:00 +0000 UTC
u2: 2015-11-26 19:00:00 +0000 UTC
s1: 1448564400


t2: 2015-11-26 19:00:00 +0200 EET
u2: 2015-11-26 17:00:00 +0000 UTC
s2: 1448557200


[{Date:2015-11-26 19:00:00 +0000 UTC} {Date:2015-11-26 17:00:00 +0000 UTC}]

Inside MongoDB you'll have the following:

> db.test.find().pretty();
{
        "_id" : ObjectId("56575627ef8a3999e44422fa"),
        "date" : ISODate("2015-11-26T19:00:00Z")
}
{
        "_id" : ObjectId("56575627ef8a3999e44422fb"),
        "date" : ISODate("2015-11-26T17:00:00Z")
}

Is this a feature or am I doing something wrong here?

Thanks,

Alex.

[Gustavo Niemeyer]

Hi Alex,

I wouldn't quite call it a feature, but more like the expected behavior. MongoDB timestamps do not carry a timezone, so mgo handles them as UTC when going back and forth.

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[al...@deefuse.com]

Hi and thanks for clearing that out for me.

I had a quick look at the code to see where the conversion happens. Am i right in saying that this is done in "bson/encode.go" lines 431 - 434?

Thanks,
Alex