diff --git a/src/parser.js b/src/parser.js
index 5f32e55..20bb5c9 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -685,7 +685,7 @@ export default class Parser extends Stream {
               }
               if (dateRange.duration && dateRange.endDate) {
                 const startDate = dateRange.startDate;
-                const newDateInSeconds = startDate.setSeconds(startDate.getSeconds() + dateRange.duration);
+                const newDateInSeconds = startDate.getTime() + (dateRange.duration * 1000);
 
                 this.manifest.dateRanges[index].endDate = new Date(newDateInSeconds);
               }
@@ -693,13 +693,20 @@ export default class Parser extends Stream {
                 dateRangeTags[dateRange.id] = dateRange;
               } else {
                 for (const attribute in dateRangeTags[dateRange.id]) {
-                  if (dateRangeTags[dateRange.id][attribute] !== dateRange[attribute]) {
+                  if (!!dateRange[attribute] && JSON.stringify(dateRangeTags[dateRange.id][attribute]) !== JSON.stringify(dateRange[attribute])) {
                     this.trigger('warn', {
-                      message: 'EXT-X-DATERANGE tags with the same ID in a playlist must have the same attributes and same attribute values'
+                      message: 'EXT-X-DATERANGE tags with the same ID in a playlist must have the same attributes values'
                     });
                     break;
                   }
                 }
+                // if tags with the same ID do not have conflicting attributes, merge them
+                const dateRangeWithSameId = this.manifest.dateRanges.findIndex((dateRangeToFind) => dateRangeToFind.id === dateRange.id);
+
+                this.manifest.dateRanges[dateRangeWithSameId] = Object.assign(this.manifest.dateRanges[dateRangeWithSameId], dateRange);
+                dateRangeTags[dateRange.id] = Object.assign(dateRangeTags[dateRange.id], dateRange);
+                // after merging, delete the duplicate dateRange that was added last
+                this.manifest.dateRanges.pop();
               }
             },
             'independent-segments'() {
diff --git a/test/parser.test.js b/test/parser.test.js
index 25f6c14..7565b32 100644
--- a/test/parser.test.js
+++ b/test/parser.test.js
@@ -1031,7 +1031,7 @@ QUnit.module('m3u8s', function(hooks) {
     );
   });
 
-  QUnit.test('warns when playlist has multiple #EXT-X-DATERANGE tag same ID but different attribute names and values', function(assert) {
+  QUnit.test('warns when playlist has multiple #EXT-X-DATERANGE tag same ID but different attribute values', function(assert) {
     this.parser.push([
       '#EXT-X-VERSION:3',
       '#EXT-X-MEDIA-SEQUENCE:0',
@@ -1041,12 +1041,12 @@ QUnit.module('m3u8s', function(hooks) {
       '#EXT-X-ENDLIST',
       '#EXT-X-PROGRAM-DATE-TIME:2017-07-31T20:35:35.053+00:00',
       '#EXT-X-DATERANGE:ID="12345",START-DATE="2023-04-13T18:16:15.840000Z",END-ON-NEXT=YES,CLASS="CLASSATTRIBUTE"',
-      '#EXT-X-DATERANGE:ID="12345",START-DATE="2023-04-13T18:16:20.840000Z"'
+      '#EXT-X-DATERANGE:ID="12345",START-DATE="2023-04-13T18:16:15.840000Z",CLASS="CLASSATTRIBUTE1"'
     ].join('\n'));
     this.parser.end();
 
     const warnings = [
-      'EXT-X-DATERANGE tags with the same ID in a playlist must have the same attributes and same attribute values'
+      'EXT-X-DATERANGE tags with the same ID in a playlist must have the same attributes values'
     ];
 
     assert.deepEqual(
@@ -1095,7 +1095,33 @@ QUnit.module('m3u8s', function(hooks) {
     );
   });
 
-  QUnit.test(' playlist with multiple ext-x-daterange ', function(assert) {
+  QUnit.test('playlist with multiple ext-x-daterange with same ID but no conflicting attributes', function(assert) {
+    const expectedDateRange = {
+      id: '12345',
+      scte35In: '0xFC30200FFF2',
+      scte35Out: '0xFC30200FFF2',
+      startDate: new Date('2023-04-13T18:16:15.840000Z'),
+      class: 'CLASSATTRIBUTE'
+    };
+
+    this.parser.push([
+      '#EXT-X-VERSION:3',
+      '#EXT-X-MEDIA-SEQUENCE:0',
+      '#EXT-X-DISCONTINUITY-SEQUENCE:0',
+      '#EXTINF:10,',
+      'media-00001.ts',
+      '#EXT-X-ENDLIST',
+      '#EXT-X-PROGRAM-DATE-TIME:2017-07-31T20:35:35.053+00:00',
+      '#EXT-X-DATERANGE:ID="12345",SCTE35-IN=0xFC30200FFF2,START-DATE="2023-04-13T18:16:15.840000Z",CLASS="CLASSATTRIBUTE"',
+      '#EXT-X-DATERANGE:ID="12345",SCTE35-OUT=0xFC30200FFF2,START-DATE="2023-04-13T18:16:15.840000Z"'
+    ].join('\n'));
+    this.parser.end();
+    assert.equal(this.parser.manifest.dateRanges.length, 1, 'two dateranges with same ID are merged');
+    assert.deepEqual(this.parser.manifest.dateRanges[0], expectedDateRange);
+
+  });
+
+  QUnit.test('playlist with multiple ext-x-daterange ', function(assert) {
     this.parser.push([
       ' #EXTM3U',
       '#EXT-X-VERSION:6',