Daily Archives: May 25, 2006

I’ve recently had cause to parse some date values in Java. As a
result I’ve produced a class which can manage to parse an awful lot of
date formats. I thought I’d better document it in case someone found it
useful. Certainly there doesn’t appear to be anything elsewhere which
shows you how to parse lots of formats. I have found the order of
date_formats to be very brittle, so I don’t recommend you
change it without an awful lot of test cases.

Anyway, without further to do, I present to you, the Pathological
Date Parser for Java

// Copyright 2006 David Pashley <david@davidpashley.com>
// Licensed under the GPL version 2
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.TimeZone;

public class Date {
    private Calendar date;

    static String[] date_formats = {
            "yyyy-MM-dd'T'kk:mm:ss'Z'",        // ISO
            "yyyy-MM-dd'T'kk:mm:ssz",          // ISO
            "yyyy-MM-dd'T'kk:mm:ss",           // ISO
            "EEE, d MMM yy kk:mm:ss z",        // RFC822
            "EEE, d MMM yyyy kk:mm:ss z",      // RFC2882
            "EEE MMM  d kk:mm:ss zzz yyyy",    // ASC
            "EEE, dd MMMM yyyy kk:mm:ss",   //Disney Mon, 26 January 2004 16:31:00 ET
            "-yy-MM",
            "-yyMM",
            "yy-MM-dd",
            "yyyy-MM-dd",
            "yyyy-MM",
            "yyyy-D",
            "-yyMM",
            "yyyyMMdd",
            "yyMMdd",
            "yyyy",
            "yyD"

    };
    public Date(String d) {
        SimpleDateFormat formatter = new SimpleDateFormat();
        d = d.replaceAll("([-+]\d\d:\d\d)", "GMT$1"); // Correct W3C times
        d = d.replaceAll(" ([ACEMP])T$", " $1ST"); // Correct Disney timezones
        for (int i = 0; i < date_formats.length; i++) {
           try {
              formatter.applyPattern(date_formats[i]);
              formatter.parse(d);
              date = formatter.getCalendar();
              break;
           } catch(Exception e) {
              // Oh well. We tried
           }
        }

    }
}

The only date formats I can’t get it to parse are <4-digit
year>-<day of year> and <2digit year><day of
year> (e.g. 2003-335 and 03335 for
2003-12-01). If you can add support for those and other date formats
I’ll gladly take patches.