Getting GMT time with Android

Question

I have been digging into the question for a while in StackOverflow Android get Current UTC time and How can I get the current date and time in UTC or GMT in Java?

I have tried two ways to get the current time of my phone in GMT. I am in Spain and the difference is GMT+2. So let's see with an example: 1º attemp: I created a format and applied it to System.currentTimeMillis();

    DateFormat dfgmt = new java.text.SimpleDateFormat("yyyy-MM-dd hh:mm:ss");   
    dfgmt.setTimeZone(TimeZone.getTimeZone("GMT")); 
    String gmtTime = dfgmt.format(new Date());
    //Using System.currentTimeMillis() is the same as new Date()
    Date dPhoneTime = dfgmt.parse(gmtTime);
    Long phoneTimeUTC = dPhoneTime.getTime();

I need to substract that time to another time, that's why i do the cast to Long.

    DateFormat df = new java.text.SimpleDateFormat("yyyy-MM-dd hh:mm:ss");          
    Date arrivalDate = df.parse(item.getArrivalDate());
    //the String comes from JSON and is for example:"UTC_arrival":"2011-05-16 18:00:00"
    //which already is in UTC format. So the DateFormat doesnt have the GMT paramater as dfgmt
    diff = arrival.getTime() - phoneTimeUTC ;

I also tried this:

    Calendar aGMTCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
    Long phoneTimeUTC = aGMTCalendar.getTimeInMillis()

And still I dont get the right difference. But if I do this:

    Long phoneTimeUTC = aGMTCalendar.getTimeInMillis()-3600000*2;

It does work OK.

Any ideas?

Thanks a lot,

David.

Answer 1

As far as I read the calendar.getTimeInMillis(); returns the UTC time in millis. I used the following code and compared it to the Epoch in this site 

public int GetUnixTime()
{
    Calendar calendar = Calendar.getInstance();
    long now = calendar.getTimeInMillis();
    int utc = (int)(now / 1000);
    return (utc);

}

Giora

Answer 2

you can always use:

Calendar mCalendar = Calendar.getInstance(TimeZone.getTimeZone("gmt"));
long millies = mCalendar.getTimeInMillis();

or

Calendar mCalendar = Calendar.getInstance(TimeZone.getTimeZone("utc"));
long millies = mCalendar.getTimeInMillis();

Answer 3

Output: 2016-08-01 14:37:48 UTC

    final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss z");
    dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));

Works fine.

Answer 4

This works for sure!

        SimpleDateFormat dateFormatGmt = new SimpleDateFormat("dd:MM:yyyy HH:mm:ss");
        dateFormatGmt.setTimeZone(TimeZone.getTimeZone("GMT"));
        System.out.println(dateFormatGmt.format(new Date())+"");

Specify the format, and you will get it in GMT!

Answer 5

     Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
     Date currentLocalTime = cal.getTime();
     DateFormat date = new SimpleDateFormat("dd-MM-yyy HH:mm:ss z");   
     date.setTimeZone(TimeZone.getTimeZone("GMT")); 
     String localTime = date.format(currentLocalTime); 
     System.out.println(localTime);

Have a look and see if that works.