/*

  * Copyright 1999,2004 The Apache Software Foundation.

  * 

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  * 

  *      http://www.apache.org/licenses/LICENSE-2.0

  * 

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package org.apache.commons.feedparser.tools;

 import java.text.SimpleDateFormat;

 import java.util.Date;

 import java.util.Locale;

 import java.util.TimeZone;

 /**

  *

  * RFC 822 date parsing utility.  Designed for parsing the ISO subset used in

  * Dublin Core, RSS 1.0, and Atom.

  *

  * 

  http://asg.web.cmu.edu/rfc/rfc822.html#sec-5

  * 

  5.1 SYNTAX

  * 

  * date-time   =  [ day "," ] date time        ; dd mm yy

  * ;  hh:mm:ss zzz

  * 

  * day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"

  * /  "Fri"  / "Sat" /  "Sun"

  * 

  * date        =  1*2DIGIT month 2DIGIT        ; day month year

  * ;  e.g. 20 Jun 82

  * 

  * month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"

  * /  "May"  /  "Jun" /  "Jul"  /  "Aug"

  * /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"

  * 

  * time        =  hour zone                    ; ANSI and Military

  * 

  * hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]

  * ; 00:00:00 - 23:59:59

  * 

  * zone        =  "UT"  / "GMT"                ; Universal Time

  * ; North American : UT

  * /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4

  * /  "CST" / "CDT"                ;  Central:  - 6/ - 5

  * /  "MST" / "MDT"                ;  Mountain: - 7/ - 6

  * /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7

  * /  1ALPHA                       ; Military: Z = UT;

  * ;  A:-1; (J not used)

  * ;  M:-12; N:+1; Y:+12

  * / ( ("+" / "-") 4DIGIT )        ; Local differential

  * ;  hours+min. (HHMM)

  * 

  5.2 SEMANTICS

  * 

  * If included, day-of-week must be the day implied by the date specification.

  * 

  * Time zone may be indicated in several ways. "UT" is Univer- sal Time

  * (formerly called "Greenwich Mean Time"); "GMT" is per- mitted as a reference

  * to Universal Time. The military standard uses a single character for each

  * zone. "Z" is Universal Time. "A" indicates one hour earlier, and "M"

  * indicates 12 hours ear- lier; "N" is one hour later, and "Y" is 12 hours

  * later. The letter "J" is not used. The other remaining two forms are taken

  * from ANSI standard X3.51-1975. One allows explicit indication of the amount

  * of offset from UT; the other uses common 3-character strings for indicating

  * time zones in North America.

  * 

  * 

  * 

  * @author <a href="mailto:burton@apache.org">Kevin A. Burton (burtonator)</a>

  * @version $Id: RFC822DateParser.java 373572 2006-01-30 19:28:41Z mvdb $

  */

 public class RFC822DateParser {

     private static SimpleDateFormat df

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

     public static Date parse( String input ) throws java.text.ParseException {

         //NOTE: SimpleDateFormat uses GMT[-+]hh:mm for the TZ which breaks

         //things a bit.  Before we go on we have to repair this.

         return df.parse( input );

     }

     public static String toString( Date date, TimeZone tz ) {

         df.setTimeZone( tz );

         return df.format( date );

     }

 }