Android SimpleDateFormat, how to use it?

I am trying to use the Android SimpleDateFormat like this:

String _Date = "2010-09-29 08:45:22"
SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");

try {
    Date date = fmt.parse(_Date);
    return fmt.format(date);
}
catch(ParseException pe) {
    return "Date";    
}

The result is good and I have: 2010-09-29

But if I change the SimpleDateFormat to

SimpleDateFormat("dd-MM-yyyy");

the problem is that I will got 03-03-0035 !!!!

Why and how to get the format like dd-MM-yyyy?

I assume you would like to reverse the date format?

SimpleDateFormat can be used for parsing and formatting. You just need two formats, one that parses the string and the other that returns the desired print out:

SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
Date date = fmt.parse(dateString);

SimpleDateFormat fmtOut = new SimpleDateFormat("dd-MM-yyyy");
return fmtOut.format(date);

Since Java 8:

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyy-MM-dd").withZone(ZoneOffset.UTC);
TemporalAccessor date = fmt.parse(dateString);
Instant time = Instant.from(date);

DateTimeFormatter fmtOut = DateTimeFormatter.ofPattern("dd-MM-yyyy").withZone(ZoneOffset.UTC);
return fmtOut.format(time);

Below is all date formats available, read more doc here.

Symbol	Meaning                Kind      	Example
D	    day in year	            Number	      189
E	    day of week	            Text	      E/EE/EEE:Tue, EEEE:Tuesday, EEEEE:T
F	    day of week in month    Number	      2 (2nd Wed in July)
G	    era designator	        Text	      AD
H	    hour in day (0-23)	    Number	      0
K	    hour in am/pm (0-11)	Number	      0
L	    stand-alone month	    Text	      L:1 LL:01 LLL:Jan LLLL:January LLLLL:J
M	    month in year	        Text	      M:1 MM:01 MMM:Jan MMMM:January MMMMM:J
S	    fractional seconds	    Number	      978
W	    week in month	        Number	      2
Z	    time zone (RFC 822)	    Time Zone	  Z/ZZ/ZZZ:-0800 ZZZZ:GMT-08:00 ZZZZZ:-08:00
a	    am/pm marker	        Text	      PM
c	    stand-alone day of week	Text	      c/cc/ccc:Tue, cccc:Tuesday, ccccc:T
d	    day in month	        Number	      10
h	    hour in am/pm (1-12)	Number	      12
k	    hour in day (1-24)	    Number	      24
m	    minute in hour	        Number	      30
s	    second in minute	    Number	      55
w	    week in year	        Number	      27
G	    era designator	        Text	      AD
y	    year	                Number	      yy:10 y/yyy/yyyy:2010
z	    time zone	            Time Zone	  z/zz/zzz:PST zzzz:Pacific Standard 

I think this Link might helps you

OR

    Date date = Calendar.getInstance().getTime();
    //
    // Display a date in day, month, year format
    //
    DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
    String today = formatter.format(date);
    System.out.println("Today : " + today);
     

String _Date = "2010-09-29 08:45:22"
SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat fmt2 = new SimpleDateFormat("dd-MM-yyyy");
    try {
        Date date = fmt.parse(_Date);
        return fmt2.format(date);
    }
    catch(ParseException pe) {

        return "Date";    
    }

try this.

Using the date-time API of java.util and their formatting API, SimpleDateFormat I have come across surprises several times but this is the biggest one! 

Given below is the illustration of what you have described in your question:

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

class Main {
	public static void main(String[] args) {
		System.out.println(formatDateWithPattern1("2010-09-29 08:45:22"));
		System.out.println(formatDateWithPattern2("2010-09-29 08:45:22"));
	}

	static String formatDateWithPattern1(String strDate) {
		SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
		try {
			Date date = fmt.parse(strDate);
			return fmt.format(date);
		} catch (ParseException pe) {
			return "Date";
		}
	}

	static String formatDateWithPattern2(String strDate) {
		SimpleDateFormat fmt = new SimpleDateFormat("dd-MM-yyyy");
		try {
			Date date = fmt.parse(strDate);
			return fmt.format(date);
		} catch (ParseException pe) {
			return "Date";
		}
	}
}

Output:

2010-09-29
03-03-0035

Surprisingly, SimpleDateFormat silently performed the parsing and formatting without raising an alarm. Anyone reading this will not have a second thought to stop using them completely and switch to the modern date-time API.

For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7.

If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.

Using the modern date-time API:

Since the pattern used in both the functions are wrong as per the input string, the parser should raise the alarm and the parsing/formatting types of the modern date-time API do it responsibly.

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;

class Main {
	public static void main(String[] args) {
		System.out.println(formatDateWithPattern1("2010-09-29 08:45:22"));
		System.out.println(formatDateWithPattern2("2010-09-29 08:45:22"));
	}

	static String formatDateWithPattern1(String strDate) {
		DateTimeFormatter dtf = DateTimeFormatter.ofPattern("uuuu-MM-dd");
		try {
			LocalDateTime date = LocalDateTime.parse(strDate, dtf);
			return dtf.format(date);
		} catch (DateTimeParseException dtpe) {
			return "Date";
		}
	}

	static String formatDateWithPattern2(String strDate) {
		DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd-MM-uuuu");
		try {
			LocalDateTime date = LocalDateTime.parse(strDate, dtf);
			return dtf.format(date);
		} catch (DateTimeParseException dtpe) {
			return "Date";
		}
	}
}

Output:

Date
Date

Moral of the story

1. The date-time API of java.util and their formatting API, SimpleDateFormat are outdated and error-prone. Stop using them completely and switch to the modern date-time API. Learn about the modern date-time API at Trail: Date Time.
2. Stick to the format in your input date-time string while parsing it. If you want the output in a different format, use a differnt instance of the parser/formatter class.

Demo:

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

class Main {
	public static void main(String[] args) {
		String strDateTime = "2010-09-29 08:45:22";
		DateTimeFormatter dtfForParsing = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss");
		LocalDateTime ldt = LocalDateTime.parse(strDateTime, dtfForParsing);
		System.out.println(ldt);// The default format as returned by LocalDateTime#toString

		// Some custom formats for output
		System.out.println("########In custom formats########");
		DateTimeFormatter dtfForFormatting1 = DateTimeFormatter.ofPattern("dd-MM-uuuu HH:mm:ss");
		DateTimeFormatter dtfForFormatting2 = DateTimeFormatter.ofPattern("dd-MM-uuuu");
		DateTimeFormatter dtfForFormatting3 = DateTimeFormatter.ofPattern("'Day: 'EEEE, 'Date: 'MMMM dd uuuu");
		System.out.println(dtfForFormatting1.format(ldt));
		System.out.println(dtfForFormatting2.format(ldt));
		System.out.println(dtfForFormatting3.format(ldt));
		System.out.println("################################");
	}
}

Output:

2010-09-29T08:45:22
########In custom formats########
29-09-2010 08:45:22
29-09-2010
Day: Wednesday, Date: September 29 2010
################################

This worked for me...

@SuppressLint("SimpleDateFormat")
private void setTheDate() {
	long msTime = System.currentTimeMillis();
	Date curDateTime = new Date(msTime);
	SimpleDateFormat formatter = new SimpleDateFormat("MM'/'dd'/'y hh:mm");
	curDate = formatter.format(curDateTime);
	mDateText.setText("" + curDate);
}

java.time and desugaring

I recommend that you use java.time, the modern Java date and time API, for your date work. First define a formatter for your string:

private static DateTimeFormatter formatter
		= DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss");

Then do:

	String dateString = "2010-09-29 08:45:22";
	LocalDateTime dateTime = LocalDateTime.parse(dateString, formatter);
	String newString = dateTime.format(DateTimeFormatter.ISO_LOCAL_DATE);
	System.out.println(newString);

Output is:

> 2010-09-29

I find it a good practice to parse the entire string even though we currently have no use for the time of day. That may come some other day. java.time furnishes a predefined formatter for your first output format, DateTimeFormatter.ISO_LOCAL_DATE. If you want the opposite order of day, month and year, we will need to write our own formatter for that:

private static DateTimeFormatter dateFormatter
		= DateTimeFormatter.ofPattern("dd-MM-uuuu");

Then we can obtain that too:

	String dmyReversed = dateTime.format(dateFormatter);
	System.out.println(dmyReversed);

> 29-09-2010

What went wrong in your code?

> the problem is that I will got 03-03-0035 !!!!

This is how confusing a SimpleDateFormat with standard settings is: With format pattern dd-MM-yyyy it parses 2010-09-29 as the 2010th day of month 9 of year 29. Year 29 AD that is. And it doesn’t disturb it that there aren’t 2010 days in September. It just keeps counting days through the following months and years and ends up five and a half years later, on 3 March year 35.

Which is just a little bit of the reason why I say: don’t use that class.

Question: Doesn’t java.time require Android API level 26?

java.time works nicely on both older and newer Android devices. 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 non-Android 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.

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.
• uuuu versus yyyy in DateTimeFormatter formatting pattern codes in Java?
• Wikipedia article: ISO 8601

Here is an easy example of SimpleDateFormat tried in Android Studio 3 and Java 9:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd", Locale.US); 
String strDate = sdf.format(strDate);

> Note: > SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); shows > some deprecation warning in Android Studio 3 Lint. So, add a second > parameter Locale.US to specify the Localization in date formatting.

It took a lot of efforts. I did a lot of hit and trial and finally I got the solution. I had used ""MMM"" for showing month as: JAN

If you looking for date, month and year separately

or how to use letters from answer of heloisasim

    SimpleDateFormat day = new SimpleDateFormat("d");
    SimpleDateFormat month = new SimpleDateFormat("M");
    SimpleDateFormat year = new SimpleDateFormat("y");

    Date d = new Date();
    String dayS = day.format(d);
    String monthS = month.format(d);
    String yearS = year.format(d);

public String formatDate(String dateString) {
    SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
    Date date = null;
    try {
        date = fmt.parse(dateString);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    SimpleDateFormat fmtOut = new SimpleDateFormat("dd-MM-yyyy");
    return fmtOut.format(date);
}