fix(date filter): display localised era for G format codes

This implementation is limited to displaying only AD (CE) years correctly,
since we do not support the `u` style year format that can be used to represent
dates before 1 AD.

Closes #10503
Closes #11266

Author: petebacondarwin

src/ng/filter/filters.js

@@ -302,6 +302,14 @@ function ampmGetter(date, formats) {
   return date.getHours() < 12 ? formats.AMPMS[0] : formats.AMPMS[1];
 }
 
+function eraGetter(date, formats) {
+  return date.getFullYear() <= 0 ? formats.ERAS[0] : formats.ERAS[1];
+}
+
+function longEraGetter(date, formats) {
+  return date.getFullYear() <= 0 ? formats.ERANAMES[0] : formats.ERANAMES[1];
+}
+
 var DATE_FORMATS = {
   yyyy: dateGetter('FullYear', 4),
     yy: dateGetter('FullYear', 2, 0, true),
@@ -328,10 +336,14 @@ var DATE_FORMATS = {
      a: ampmGetter,
      Z: timeZoneGetter,
     ww: weekGetter(2),
-     w: weekGetter(1)
+     w: weekGetter(1),
+     G: eraGetter,
+     GG: eraGetter,
+     GGG: eraGetter,
+     GGGG: longEraGetter
 };
 
-var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d+|H+|h+|m+|s+|a|Z|w+))(.*)/,
+var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEwG']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d+|H+|h+|m+|s+|a|Z|G+|w+))(.*)/,
     NUMBER_STRING = /^\-?\d+$/;
 
 /**
@@ -368,6 +380,8 @@ var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d
  *   * `'Z'`: 4 digit (+sign) representation of the timezone offset (-1200-+1200)
  *   * `'ww'`: Week of year, padded (00-53). Week 01 is the week with the first Thursday of the year
  *   * `'w'`: Week of year (0-53). Week 1 is the week with the first Thursday of the year
+ *   * `'G'`, `'GG'`, `'GGG'`: The abbreviated form of the era string (e.g. 'AD')
+ *   * `'GGGG'`: The long form of the era string (e.g. 'Anno Domini')
  *
  *   `format` string can also be one of the following predefined
  *   {@link guide/i18n localizable formats}:

test/ng/filter/filtersSpec.js

@@ -298,6 +298,18 @@ describe('filters', function() {
 
       expect(date(earlyDate, "MMMM dd, y")).
                       toEqual('September 03, 1');
+
+      expect(date(noon, "MMMM dd, y G")).
+                      toEqual('September 03, 2010 AD');
+
+      expect(date(noon, "MMMM dd, y GG")).
+                      toEqual('September 03, 2010 AD');
+
+      expect(date(noon, "MMMM dd, y GGG")).
+                      toEqual('September 03, 2010 AD');
+
+      expect(date(noon, "MMMM dd, y GGGG")).
+                      toEqual('September 03, 2010 Anno Domini');
     });
 
     it('should accept negative numbers as strings', function() {