feat(filter): allow to define the timezone for formatting dates

Angular used to always use the browser timezone for
`dateFilter`. An additional parameter was added to allow to use
`UTC` timezone instead.

Related to #8447.

Author: tbosch

src/ng/filter/filters.js

@@ -362,6 +362,8 @@ var DATE_FORMATS_SPLIT = /((?:[^yMdHhmsaZEw']+)|(?:'(?:[^']|'')*')|(?:E+|y+|M+|d
  *    specified in the string input, the time is considered to be in the local timezone.
  * @param {string=} format Formatting rules (see Description). If not specified,
  *    `mediumDate` is used.
+ * @param {string=} timezone Timezone to be used for formatting. Right now, only `'UTC'` is supported.
+ *    If not specified, the timezone of the browser will be used.
  * @returns {string} Formatted string or the input if input is not recognized as date/millis.
  *
  * @example
@@ -421,7 +423,7 @@ function dateFilter($locale) {
   }
 
 
-  return function(date, format) {
+  return function(date, format, timezone) {
     var text = '',
         parts = [],
         fn, match;
@@ -451,6 +453,10 @@ function dateFilter($locale) {
       }
     }
 
+    if (timezone && timezone === 'UTC') {
+      date = new Date(date.getTime());
+      date.setMinutes(date.getMinutes() + date.getTimezoneOffset());
+    }
     forEach(parts, function(value){
       fn = DATE_FORMATS[value];
       text += fn ? fn(date, $locale.DATETIME_FORMATS)

test/ng/filter/filtersSpec.js

@@ -390,5 +390,10 @@ describe('filters', function() {
       expect(date('2003-09-10T13:02:03.12Z', format)).toEqual('2003-09-' + localDay + ' 03');
       expect(date('2003-09-10T13:02:03.1Z', format)).toEqual('2003-09-' + localDay + ' 03');
     });
+
+    it('should use UTC if the timezone is set to "UTC"', function() {
+      expect(date(new Date(2003, 8, 10, 3, 2, 4), 'yyyy-MM-dd HH-mm-ss')).toEqual('2003-09-10 03-02-04');
+      expect(date(new Date(Date.UTC(2003, 8, 10, 3, 2, 4)), 'yyyy-MM-dd HH-mm-ss', 'UTC')).toEqual('2003-09-10 03-02-04');
+    });
   });
 });