Fix off-by-one error in computing the quarter in date formatting

pkg/intl/lib/src/date_format_field.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.
 
 part of intl;
 
 /**
  * This is a private class internal to DateFormat which is used for formatting
  * particular fields in a template. e.g. if the format is hh:mm:ss then the
  * fields would be "hh", ":", "mm", ":", and "ss". Each type of field knows
@@ skipping 327 matching lines @@
     switch(width) {
       case 5: possibilities = symbols.STANDALONENARROWMONTHS; break;
       case 4: possibilities = symbols.STANDALONEMONTHS; break;
       case 3: possibilities = symbols.STANDALONESHORTMONTHS; break;
       default: return handleNumericField(input, dateFields.setMonth);
     }
     dateFields.month = parseEnumeratedString(input, possibilities) + 1;
   }
 
   String formatQuarter(DateTime date) {
-    var quarter = (date.month / 3).truncate();
+    var quarter = ((date.month - 1) / 3).truncate();
     if (width < 4) {
       return symbols.SHORTQUARTERS[quarter];
     } else {
       return symbols.QUARTERS[quarter];
     }
   }
   String formatDayOfMonth(DateTime date) {
     return padTo(width, date.day);
   }
 
@@ skipping 38 matching lines @@
     var basicString = toBePrinted.toString();
     if (basicString.length >= width) return basicString;
     var buffer = new StringBuffer();
     for (var i = 0; i < width - basicString.length; i++) {
       buffer.write('0');
      }
     buffer.write(basicString);
     return buffer.toString();
   }
 }