Date formatting based on user locale on android

While the accepted answer was correct when the question was asked, it has later become outdated. I am contributing the modern answer.

java.time and ThreeTenABP

    DateTimeFormatter dateFormatter = DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT);
    
    LocalDate dateOfBirth = LocalDate.of(1991, Month.OCTOBER, 13);
    String formattedDob = dateOfBirth.format(dateFormatter);
    System.out.println("Born: " + formattedDob);

It gives different output depending on the locale setting of the JVM (usually taking from the device). For example:

• Canadian French: Born: 91-10-13
• Chinese: Born: 1991/10/13
• German: Born: 13.10.91
• Italian: Born: 13/10/91

If you want a longer format, you may specify a different format style. Example outputs in US English locale:

• FormatStyle.SHORT: Born: 10/13/91
• FormatStyle.MEDIUM: Born: Oct 13, 1991
• FormatStyle.LONG: Born: October 13, 1991
• FormatStyle.FULL: Born: Thursday, October 13, 1991

Question: Can I use java.time on Android?

DateTimeFormatter.ofLocalizedDate requires Api O minimum.

Yes, java.time works nicely on older and newer Android devices. No, it does not require API level 26 or Oreo even though a message in your Android Studio might have you think that. It just requires at least Java 6.

• In Java 8 and later and on newer Android devices (from API level 26) the modern API comes built-in.
• In Java 6 and 7 get the ThreeTen Backport, the backport of the modern classes (ThreeTen for JSR 310; see the links at the bottom).
• On older Android either use desugaring or the Android edition of ThreeTen Backport. It’s called ThreeTenABP. In the latter case make sure you import the date and time classes from org.threeten.bp with subpackages.

Question: Can I also accept user input in the user’s local format?

Yes, you can. The formatter can also be used for parsing a string from the user into a LocalDate:

    LocalDate date = LocalDate.parse(userInputString, dateFormatter);

I suggest that you first format an example date and show it to the user so that s/he can see which format your program expects for his/her locale. As example date take a date with day of month greater than 12 and year greater than 31 so that the order of day, month and year can be seen from the example (for longer formats the year doesn’t matter since it will be four digits).

Parsing will throw a DateTimeParseException if the user entered the date in an incorrect format or a non-valid date. Catch it and allow the user to try again.

Question: Can I do likewise with a time of day? A date and time?

Yes. For formatting a time of day according to a user’s locale, get a formatter from DateTimeFormatter.ofLocalizedTime. For both date and time together use one of the overloaded versions of DateTimeFormatter.ofLocalizedDateTime.

Avoid the DateFormat, SImpleDateFormat and Date classes

I recommend you don’t use DateFormat, SimpleDateFormat and Date. Those classes are poorly designed and long outdated, the first two in particular notoriously troublesome. Instead use LocalDate, DateTimeFormatter and other classes from java.time, the modern Java date and time API.

Links

• Oracle tutorial: Date Time explaining how to use java.time.
• Java Specification Request (JSR) 310, where java.time was first described.
• ThreeTen Backport project, the backport of java.time to Java 6 and 7 (ThreeTen for JSR-310).
• Java 8+ APIs available through desugaring
• ThreeTenABP, Android edition of ThreeTen Backport
• Question: How to use ThreeTenABP in Android Project, with a very thorough explanation.

You can use the DateFormat class that formats a date according to the user locale.

Example:

String dateOfBirth = "26/02/1974";
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Date date = null;
try {
    date = sdf.parse(dateOfBirth);
} catch (ParseException e) {
    // handle exception here !
}
java.text.DateFormat dateFormat = android.text.format.DateFormat.getDateFormat(context);
String s = dateFormat.format(date);

You can use the different methods getLongDateFormat, getMediumDateFormat depending on the level of verbosity you would like to have.