Java simpledateformat returns zero for month

Question

This is a possible duplicate, but I'm not able to figure out why the month is returned as zero when specified as MMM and works well with mm(numeric). Any help here would be really appreciated?

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Base64;
import java.util.Date;
import java.util.Locale;

 public class time1 {

 public static void main(String[] args) {

    DateFormat originalFormat = new SimpleDateFormat("dd-MMM-yyyy", Locale.ENGLISH);
    DateFormat targetFormat = new SimpleDateFormat("yyyy-mm-dd");
    Date date = null;
    try {
            date = originalFormat.parse("26-Aug-2011");
    } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
    }
    String formattedDate = targetFormat.format(date);
    System.out.println("old date: " + date);
    System.out.println("new date: " + formattedDate);
 }
}

The output is:

old date: Fri Aug 26 00:00:00 IST 2011
new date: 2011-00-26

When the format is changed to dd-mm-yyyy and the date is 26-08-2011, the output is

old date: Wed Jan 26 00:07:00 IST 2011
new date: 2011-07-26

I'm not able to understand the reason it fails with MMM, all my dates are in the format(26-Aug-2011) and I need to convert them to yyyy-mm-dd (26-07-2011).

FYI, the troublesome old date-time classes such as [`java.util.Date`](https://docs.oracle.com/javase/8/docs/api/java/util/Date.html), [`java.util.Calendar`](https://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html), and `java.text.SimpleDateFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [java.time](https://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html) classes. See [Tutorial by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). — Basil Bourque, Sep 22 '17 at 17:11

score 11 · Accepted Answer · edited Sep 26 '17 at 11:40

11

From the documentation, I can say that

DateFormat targetFormat = new SimpleDateFormat("yyyy-mm-dd");

needs to be changed to

DateFormat targetFormat = new SimpleDateFormat("yyyy-MM-dd");
// this gives you the Date in Digits.

As per documentation,

'M' is used for Month in Year, whereas
'm' is used for Minute in Hour.

Hence, your 'mm' is returning the Minutes which it takes as 00:00 by default which is the output you have been getting. This will give you the following Output.

old date: Fri Aug 26 00:00:00 IST 2011
new date: 2011-08-26

edited Sep 26 '17 at 11:40

Ole V.V.

81,772
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answered Sep 22 '17 at 05:18

Kaustubh Kallianpur

349
2
16

yyyy-MMM-dd is the format for "26-Aug-2011". Any change in the format gives me parse error. – user3616977 Sep 22 '17 at 05:21
please check the updated answer. You had to change the -mm- from targetformat to -MM-.. – Kaustubh Kallianpur Sep 22 '17 at 05:27
no problem :) please accept answer if you found it to be working :) – Kaustubh Kallianpur Sep 22 '17 at 05:29

score 4 · Answer 2 · answered Sep 22 '17 at 17:15

java.time

You are using troublesome old date-time classes that are now legacy, supplanted by the java.time classes.

String input = "26-Aug-2011" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd-MMM-uuuu" , Locale.US ) ;
LocalDate ld = LocalDate.parse( input , f ) ;

You desired output format of YYYY-MM-DD happens to comply with the ISO 8601 standard. The java.time classes use the standard formats by default when parsing/generating strings.

String output = ld.toString() ;

2011-08-26

See this code run live at IdeOne.com.

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

Java SE 8, Java SE 9, and later
- Built-in.
- Part of the standard Java API with a bundled implementation.
- Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
- Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
- The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
- See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Java simpledateformat returns zero for month

2 Answers2

java.time

About java.time