Firebase TIMESTAMP to date and Time

问题:

I am using firebase for my chat application. In chat object I am adding time stamp using Firebase.ServerValue.TIMESTAMP method.

I need to show the message received time in my chat application using this Time stamp .

if it's current time i need to show the time only.It's have days difference i need to show the date and time or only date.

I used the following code for convert the Firebase time stamp but i not getting the actual time.

var timestamp = '1452488445471';
var myDate = new Date(timestamp*1000);
var formatedTime=myDate.toJSON();

Please suggest the solution for this issue

回答1:

Firebase.ServerValue.TIMESTAMP is not actual timestamp it is constant that will be replaced with actual value in server if you have it set into some variable.

mySessionRef.update({ startedAt: Firebase.ServerValue.TIMESTAMP });
mySessionRef.on('value', function(snapshot){ console.log(snapshot.val()) })
//{startedAt: 1452508763895}

if you want to get server time then you can use following code

  fb.ref("/.info/serverTimeOffset").on('value', function(offset) {
    var offsetVal = offset.val() || 0;
    var serverTime = Date.now() + offsetVal;
  });

回答2:

In fact, it only work to me when used

firebase.database.ServerValue.TIMESTAMP

With one 'database' more on namespace.

回答3:

For those looking for the Firebase Firstore equivalent. It's

firebase.firestore.FieldValue.serverTimestamp()

e.g.

firebase.firestore().collection("cities").add({
    createdAt: firebase.firestore.FieldValue.serverTimestamp(),
    name: "Tokyo",
    country: "Japan"
})
.then(function(docRef) {
    console.log("Document written with ID: ", docRef.id);
})
.catch(function(error) {
    console.error("Error adding document: ", error);
});

Docs

回答4:

Solution for newer versions of Firebase (after Jan 2016)

The proper way to attach a timestamp to a database update is to attach a placeholder value in your request. In the example below Firebase will replace the createdAt property with a timestamp:

firebaseRef = firebase.database().ref();
firebaseRef.set({
  foo: "bar", 
  createdAt: firebase.database.ServerValue.TIMESTAMP
});

According to the documentation, the value firebase.database.ServerValue.TIMESTAMP is: "A placeholder value for auto-populating the current timestamp (time since the Unix epoch, in milliseconds) by the Firebase Database servers."

回答5:

It is simple. Use that function to get server timestamp as milliseconds one time only:

var getServerTime = function( cb ) {
    this.db.ref( '.info/serverTimeOffset' ).once( 'value', function( snap ) {
      var offset = snap.val();

      // Get server time by milliseconds
      cb( new Date().getTime() + offset );
    });
};

Now you can use it anywhere like that:

getServerTime( function( now ) {
    console.log( now );
});

---

Why use this way?

According to latest Firebase documentation, you should convert your Firebase timestamp into milliseconds. So you can use estimatedServerTimeMs variable below:

var offsetRef = firebase.database().ref(".info/serverTimeOffset");
offsetRef.on("value", function(snap) {
  var offset = snap.val();
  var estimatedServerTimeMs = new Date().getTime() + offset;
});

While firebase.database.ServerValue.TIMESTAMP is much more accurate, and preferable for most read/write operations, it can occasionally be useful to estimate the client's clock skew with respect to the Firebase Realtime Database's servers. You can attach a callback to the location /.info/serverTimeOffset to obtain the value, in milliseconds, that Firebase Realtime Database clients add to the local reported time (epoch time in milliseconds) to estimate the server time. Note that this offset's accuracy can be affected by networking latency, and so is useful primarily for discovering large (> 1 second) discrepancies in clock time.

https://firebase.google.com/docs/database/web/offline-capabilities

回答6:

First Of All Firebase.ServerValue.TIMESTAMP is not working anymore for me.

So for adding timestamp you have to use Firebase.database.ServerValue.TIMESTAMP

And the timestamp is in long millisecond format.To convert millisecond to simple dateformat .

Ex- dd/MM/yy HH:mm:ss

You can use the following code in java:

To get the timestamp value in string from the firebase database

String x = dataSnapshot.getValue (String.class);

The data is in string now. You can convert the string to long

long milliSeconds= Long.parseLong(x);

Then create SimpleDateFormat

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy HH:mm:ss");

Now convert your millisecond timestamp to ur sdf format

String dateAsString = sdf.format (milliSeconds);

After that you can parse it to ur Date variable

 date = sdf.parse (dateAsString);

回答7:

this works for me:

var timestamp   = snapshot.val().timestamp.toString().substring(0,10),
  date        = new Date(timestamp * 1000),
  datevalues  = [
                   date.getFullYear(),
                   date.getMonth()+1,
                   date.getDate(),
                   date.getHours(),
                   date.getMinutes(),
                   date.getSeconds(),
                ]; //=> [2011, 3, 25, 23, 0, 0]

Example of date: 8/11/2017 21:46

var formatDate =  datevalues[2]+"/"+datevalues[1]+"/"+datevalues[0]+ " "+datevalues[3]+":"+datevalues[4];

console.log(formatDate);

Regards

回答8:

This code is work for me

<script src="https://www.gstatic.com/firebasejs/4.5.1/firebase.js"></script>
<script>
var config = {
    apiKey: "",
    authDomain: "",
    databaseURL: "",
    projectId: "",
    storageBucket: "",
    messagingSenderId: ""
};

firebase.initializeApp(config);
var reff = firebase.database().ref('message');
reff.on('value',haveData, haveerr);
function haveData(datahave){
    var existval= datahave.val();
    var chabi=Object.keys(existval);
    for(var d2=0;d2< chabi.length;d2++){
        var r=chabi[d2];
        var exitval=existval[r].Message;
        var exitval1=existval[r].Name;
        var exit=existval[r].Email;
        var exitval2=existval[r].Subject;
        var timestamp=existval[r].timestamp;
        var sdate=new Date(timestamp);
        var Year=sdate.getFullYear();
        var month=sdate.getMonth()+1;
        var day=sdate.getDate();
        var hh=sdate.getHours();
        var mm=sdate.getMinutes();
        var ss=sdate.getSeconds();
    }
}

function haveerr(e){
     console.log(e);
}
</script>

回答9:

Firebase.ServerValue.TIMESTAMP is the same as new Date().getTime().

Convert it:

var timestamp = '1452488445471';
var myDate = new Date(timestamp).getTime();