Get name of day from timestamp in Android

Question

I have a class that when its initialized, it records the time of initialization in a private field with a public getter:

public class TestClass {

   private long mTimestamp;

    public TestClass(){
      mTimestamp = System.getCurrentMillis();
    }

    public long getTimestamp(){
          return mTimestamp;
    }
}

I also have an enum with the name of days:

public enum Days implements Serializable {
    MONDAY,
    TUESDAY,
    WEDNESDAY,
    THURSDAY,
    FRIDAY,
    SATURDAY,
    SUNDAY
}

Now the problem is in another class I have to get the timestamp and set a Days field to the day that the class was initialized:

public class OtherClass {

     public Days getDayOfInitialization(TestClass testClass){
          //how to do this?
          Date date = new Date(testClass.getTimestamp())
          Days day = Date.getDay(); //Deprecated!
          //convert to enum and return...
     }
}

The getDay() method of Date is deprecated...how should I do this?

Day in which time zone? It's Wednesday for me right now, but in Australia it's already Thursday... (You probably want to use `Calendar` - or better yet, Joda Time...) — Jon Skeet, Jul 02 '14 at 20:28
Why don't you just use [Calendar](http://developer.android.com/reference/java/util/Calendar.html)? — aProperFox, Jul 02 '14 at 20:29
@TylerOlson I couldnt find how to initialize calendar with a perviously known timestamp! — Dumbo, Jul 02 '14 at 20:32
@Sean87: Look at `Calendar.setTimeInMillis`. But you still need to think about time zones... — Jon Skeet, Jul 02 '14 at 20:34

JDJ · Answer 1 · 2014-07-02T21:10:34.767

If you just need the current day of week in a human-readable format, formatted to the current user's locale, then you could use this:

SimpleDateFormat sdf = new SimpleDateFormat("EEEE");
String dayString = sdf.format(new Date());

If their locale is "en_US", the output is:

Wednesday

If their locale is "de_DE", the output is:

Mittwoch

If their locale is "fr_FR", the output is:

mercredi

But if you need a numerical representation of the day of week (for example, you wanted to get '1' if it is Sunday or '2' if it is Monday), then you could use Calendar:

Calendar cal = Calendar.getInstance();
int dayInt = cal.get(Calendar.DAY_OF_WEEK);

mrd abd · Answer 2 · 2014-07-02T20:51:38.100

3

use Calendar:

  long timeStamp = testClass.getTimestamp();
  Calendar c = Calendar.getInstance();
  c.setTimeInMillis(timeStamp);

  int dayNum = c.get(Calendar.DAY_OF_WEEK);

  Days day = Days.values()[dayNum];

  return day;

edited Jul 02 '14 at 20:51

answered Jul 02 '14 at 20:38

mrd abd

828
10
19

score 2 · Answer 3 · edited Jul 02 '14 at 20:54

2

You should use Calendar.getInstance() method, which provide a calendar based on System Settings' TimeZone

Calendar now = Calendar.getInstance();

Then get the day of the week as an int (1 = Sunday, 2 = Monday, and so on...)

int day = now.get(Calendar.DAY_OF_WEEK);

edited Jul 02 '14 at 20:54

Chris Barlow

3,274
4
31
52

answered Jul 02 '14 at 20:36

Davide

21
1

Basil Bourque · Accepted Answer · 2014-07-04T18:27:16.913

Standard Week

You do not need that Enum as the standard for date-time (ISO 8601) defines a week as Monday to Sunday.

Joda-Time defines constants for each day-of-week name in English such as DateTimeConstants.MONDAY.

Avoid java.util.Date

You should be using Joda-Time library, as the java.util.Date and .Calendar classes are notoriously troublesome. Joda-Time works in Android according to others.

Avoid Milliseconds As Date-Time

Tracking date-time as milliseconds is less than optimal. Serializing to a ISO 8601 string is preferable. But if you must, so be it.

Time Zone Is Crucial

Time zone is crucial. Day-of-week is defined by time zone, as the comments above discussed.

If you want UTC, Joda-Time provides the constant DateTimeZone.UTC.

Joda-Time

DateTimeZone timeZone = DateTimeZone.forID( "Europe/Paris" );
DateTime dateTime = new DateTime( millisSinceEpochInUtc, timeZone );
int dayOfWeekNumber = dateTime.getDayOfWeek(); // ISO 8601 standard says Monday is 1.
DateTimeFormatter formatter = DateTimeFormat.forPattern( "EEEE" ).withLocale( java.util.Locale.ENGLISH );
String dayOfWeekName = formatter.print( dateTime );