Java - Unparseable date

I am trying to parse a date, but I am oddly getting an exception.

This is the code:

import java.util.Date;

String strDate = "Wed, 09 Feb 2011 12:34:27";
Date date;
SimpleDateFormat FORMATTER =  new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss");
try {
  date = FORMATTER.parse(strDate.trim());
  System.out.println(date);
} catch (ParseException e) {
  e.printStackTrace();
}

The exception is:

java.text.ParseException: Unparseable date: "Wed, 09 Feb 2011 12:34:27" at java.text.DateFormat.parse(DateFormat.java:337) at DateTest.main(DateTest.java:17)

I have read the documentation and I think my pattern is correct. So I don't understand...

Any idea?

Thanks!

Solution 1:

It's probably because of the default locale on your computer which is not english.

You should use:

new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss", Locale.ENGLISH);

instead.

Solution 2:

tl;dr

java.util.Date.from (

    LocalDateTime.parse( 
        "Wed, 09 Feb 2011 12:34:27" , 
        DateTimeFormatter.ofPattern( "EEE, dd MMM uuuu HH:mm:ss" , Locale.US )
    ).atZone( ZoneId.of( "America/Montreal" ) )
     .toInstant()

)

Details

The Question and other Answer both use outdated troublesome old date-time classes that are now legacy, supplanted by the java.time classes.

Using java.time

The input string lacks any indication of a time zone or offset-from-UTC. So we parse as an OffsetDateTime.

Specify a Locale to determine (a) the human language for translation of name of day, name of month, and such, and (b) the cultural norms deciding issues of abbreviation, capitalization, punctuation, separators, and such.

String input = "Wed, 09 Feb 2011 12:34:27" ;
Locale l = Locale.US ; 
DateTimeFormatter f = DateTimeFormatter.ofPattern( "EEE, dd MMM uuuu HH:mm:ss" , l ) ;
LocalDateTime ldt = LocalDateTime.parse( input , f ) ;

ldt.toString(): 2011-02-09T12:34:27

Time Zone

Both the Question and other Answer ignore the crucial issue of time zone.

The input string lacks a time zone or offset. We parsed as an LocalDateTime which is not a moment on the timeline, only a vague idea about possible moments. Like saying "Christmas begins at midnight on December 25, 2017", that has no meaning until you place it in the context of a particular time zone. Christmas comes much earlier in Auckland New Zealand than it does in Paris France, and much later still in Montréal Québec.

If you know the intended time zone, assign a ZoneId to produce a ZonedDateTime.

ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdt = ldt.atZone( z ); // Assigning a time zone to determine an actual moment on the timeline.

Converting

Best to avoid the troublesome old legacy date-time classes. But if you must interact with old code not yet updated to the java.time types, you can convert between the legacy classes and java.time. Look to new methods add to the old classes.

A java.util.Date is a moment on the timeline in UTC. So we need to extract an Instant from our ZonedDateTime. The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).

Instant instant = zdt.toInstant() ;
java.util.Date d = java.util.Date.from( instant ) ;  // Convert from java.time to legacy class.

Going the other direction.

Instant instant = d.toInstant() ;  // Convert from legacy class to java.time class.
ZonedDateTime zdt = instant.atZone( z ) ;  // Adjust from UTC into a particular time zone.

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.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, 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
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). 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.

Solution 3:

Never use SimpleDateFormat or DateTimeFormatter without a Locale

Since the given date-time is in English, you should use Locale.ENGLISH with your date-time parser; otherwise the parsing will fail in a system (computer, phone etc.) which is using a non-English type of locale.

Also, note that the date-time API of java.util and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended 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.

Demo:

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

public class Main {
    public static void main(String[] args) {
        final String strDateTime = "Wed, 09 Feb 2011 12:34:27";
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEE, dd MMM uuuu HH:mm:ss", Locale.ENGLISH);
        LocalDateTime ldt = LocalDateTime.parse(strDateTime, dtf);
        System.out.println(ldt);
    }
}

Output:

2011-02-09T12:34:27

By default, DateTimeFormatter#ofPattern uses the default FORMAT locale which the JVM sets during startup based on the host environment. Same is the case with SimpleDateFormat. I have tried to illustrate the problem through the following demo:

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

public class Main {
    public static void main(String[] args) {
        final String strDateTime = "Wed, 09 Feb 2011 12:34:27";
        DateTimeFormatter dtfWithDefaultLocale = null;

        System.out.println("JVM's Locale: " + Locale.getDefault());
        // Using DateTimeFormatter with the default Locale
        dtfWithDefaultLocale = DateTimeFormatter.ofPattern("EEE, dd MMM uuuu HH:mm:ss");
        System.out.println("DateTimeFormatter's Locale: " + dtfWithDefaultLocale.getLocale());
        System.out
                .println("Parsed with JVM's default locale: " + LocalDateTime.parse(strDateTime, dtfWithDefaultLocale));

        // Setting the JVM's default locale to Locale.FRANCE
        Locale.setDefault(Locale.FRANCE);

        // Using DateTimeFormatter with Locale.ENGLISH explicitly (recommended)
        DateTimeFormatter dtfWithEnglishLocale = DateTimeFormatter.ofPattern("EEE, dd MMM uuuu HH:mm:ss",
                Locale.ENGLISH);
        System.out.println("JVM's Locale: " + Locale.getDefault());
        System.out.println("DateTimeFormatter's Locale: " + dtfWithEnglishLocale.getLocale());
        LocalDateTime zdt = LocalDateTime.parse(strDateTime, dtfWithEnglishLocale);
        System.out.println("Parsed with Locale.ENGLISH: " + zdt);

        System.out.println("JVM's Locale: " + Locale.getDefault());
        // Using DateTimeFormatter with the default Locale
        dtfWithDefaultLocale = DateTimeFormatter.ofPattern("EEE, dd MMM uuuu HH:mm:ss");
        System.out.println("DateTimeFormatter's Locale: " + dtfWithDefaultLocale.getLocale());
        System.out
                .println("Parsed with JVM's default locale: " + LocalDateTime.parse(strDateTime, dtfWithDefaultLocale));
    }
}

Output:

JVM's Locale: en_GB
DateTimeFormatter's Locale: en_GB
Parsed with JVM's default locale: 2011-02-09T12:34:27
JVM's Locale: fr_FR
DateTimeFormatter's Locale: en
Parsed with Locale.ENGLISH: 2011-02-09T12:34:27
JVM's Locale: fr_FR
DateTimeFormatter's Locale: fr_FR
Exception in thread "main" java.time.format.DateTimeParseException: Text 'Wed, 09 Feb 2011 12:34:27' could not be parsed at index 0
    at java.base/java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:2046)
    at java.base/java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1948)
    at java.base/java.time.LocalDateTime.parse(LocalDateTime.java:492)
    at Main.main(Main.java:33)

The following demo, using SimpleDateFormat, is just for the sake of completeness:

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

public class Main {
    public static void main(String[] args) throws ParseException {
        final String strDateTime = "Wed, 09 Feb 2011 12:34:27";
        SimpleDateFormat sdf = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss", Locale.ENGLISH);
        Date date = sdf.parse(strDateTime);
        System.out.println(date);
    }
}

Output:

Wed Feb 09 12:34:27 GMT 2011