Updated message formatting to be more compatible with Dart string interpolation.

lib/i18n/date_format.dart

 /**
  * Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
  * for details. All rights reserved. Use of this source code is governed by a
  * BSD-style license that can be found in the LICENSE file.
  *
  * DateFormat is for formatting and parsing dates in a locale-sensitive 
  * manner. 
  * It allows the user to use any customized pattern to parse or format 
  * date-time strings under certain locales. Date elements that vary across 
  * locales include month name, weekname, field, order, etc.
@@ skipping 107 matching lines @@
    static final int _longTime = 5;
    static final int _mediumTime = 6;
    static final int _shortTime = 7;
    static final int _fullDateTime = 8;
    static final int _longDateTime = 9;
    static final int _mediumDateTime = 10;
    static final int _shortDateTime = 11;
     
   /**
    * Named constructors for each of the above values.
-   * These could probably be made shorter if we just set the format to the 
-   * constant and the parsing was lazy.
    */
   DateFormat.fullDate() : this.formatDefinition = _fullDate;
   DateFormat.longDate() : this.formatDefinition = _longDate;
   DateFormat.mediumDate() : this.formatDefinition = _mediumDate;
   DateFormat.shortDate() : this.formatDefinition = _shortDate;
   DateFormat.fullTime() : this.formatDefinition = _fullTime;
   DateFormat.longTime() : this.formatDefinition = _longTime;
   DateFormat.mediumTime() : this.formatDefinition = _mediumTime;
   DateFormat.shortTime() : this.formatDefinition = _shortTime;
   DateFormat.fullDateTime() : this.formatDefinition = _fullDateTime;
   DateFormat.longDateTime() : this.formatDefinition = _longDateTime;
   DateFormat.mediumDateTime() : this.formatDefinition = _mediumDateTime;
   DateFormat.shortDateTime() : this.formatDefinition = _shortDateTime;
+
+  /** 
+   * Explicit constructor given a particular format
+  **/  
+  DateFormat(this.formatDefinition);
   
-  DateFormat(this.formatDefinition);
+  /**
+   * Constructors for dates/times that use a default format.
+  **/
+  DateFormat.date() {formatDefinition = _fullDate;}
+  DateFormat.time() {formatDefinition = _fullTime;}
+  DateFormat.dateTime() {formatDefinition = _fullDateTime;}
 
   /**
    * 
    */
   String parse(String inputString) {
     return inputString;
   }
 
  /**
   * Format the given [date] object according to preset pattern and current 
   * locale and return a formated string for the given date.
   */
   String format(Date date, [TimeZone timeZone]) {
     // TODO(efortuna): optional TimeZone argument? TimeZone is deprecated...
     return date.toString();
   }
 }