diff --git a/src/NzbDrone.Core.Test/ParserTests/DateUtilFixture.cs b/src/NzbDrone.Core.Test/ParserTests/DateUtilFixture.cs
new file mode 100644
index 000000000..df2d4350c
--- /dev/null
+++ b/src/NzbDrone.Core.Test/ParserTests/DateUtilFixture.cs
@@ -0,0 +1,27 @@
+using System;
+using System.Globalization;
+using System.Threading;
+using FluentAssertions;
+using NUnit.Framework;
+using NzbDrone.Core.Parser;
+using NzbDrone.Core.Test.Framework;
+
+namespace NzbDrone.Core.Test.ParserTests
+{
+    [TestFixture]
+    public class DateUtilFixture : CoreTest
+    {
+        [TestCase("pt-BR")]
+        [TestCase("en-US")]
+        public void should_format_date_invariant(string culture)
+        {
+            Thread.CurrentThread.CurrentCulture = new CultureInfo(culture);
+
+            var dateNow = DateTime.Now;
+
+            DateTimeUtil.FromUnknown(dateNow.ToString("yyyy-MM-dd HH:mm:ss", CultureInfo.InvariantCulture))
+                .ToString(DateTimeUtil.Rfc1123ZPattern, CultureInfo.InvariantCulture)
+                .Should().Be(dateNow.ToString("ddd, dd MMM yyyy HH':'mm':'ss z", CultureInfo.InvariantCulture));
+        }
+    }
+}
diff --git a/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannBase.cs b/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannBase.cs
index b8ed63a1b..8c940bc2d 100644
--- a/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannBase.cs
+++ b/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannBase.cs
@@ -617,14 +617,14 @@ namespace NzbDrone.Core.Indexers.Cardigann
 
                         if (layout.Contains("yy") && DateTime.TryParseExact(data, layout, CultureInfo.InvariantCulture, DateTimeStyles.None, out var parsedDate))
                         {
-                            data = parsedDate.ToString(DateTimeUtil.Rfc1123ZPattern);
+                            data = parsedDate.ToString(DateTimeUtil.Rfc1123ZPattern, CultureInfo.InvariantCulture);
                         }
                         else
                         {
                             try
                             {
                                 var date = DateTimeUtil.ParseDateTimeGoLang(data, layout);
-                                data = date.ToString(DateTimeUtil.Rfc1123ZPattern);
+                                data = date.ToString(DateTimeUtil.Rfc1123ZPattern, CultureInfo.InvariantCulture);
                             }
                             catch (InvalidDateException ex)
                             {
@@ -696,10 +696,10 @@ namespace NzbDrone.Core.Indexers.Cardigann
                         break;
                     case "timeago":
                     case "reltime":
-                        data = DateTimeUtil.FromTimeAgo(data).ToString(DateTimeUtil.Rfc1123ZPattern);
+                        data = DateTimeUtil.FromTimeAgo(data).ToString(DateTimeUtil.Rfc1123ZPattern, CultureInfo.InvariantCulture);
                         break;
                     case "fuzzytime":
-                        data = DateTimeUtil.FromUnknown(data).ToString(DateTimeUtil.Rfc1123ZPattern);
+                        data = DateTimeUtil.FromUnknown(data).ToString(DateTimeUtil.Rfc1123ZPattern, CultureInfo.InvariantCulture);
                         break;
                     case "validfilename":
                         data = StringUtil.MakeValidFileName(data, '_', false);
diff --git a/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannParser.cs b/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannParser.cs
index 244b221df..91374487f 100644
--- a/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannParser.cs
+++ b/src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannParser.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Net;
 using System.Text.RegularExpressions;
@@ -509,7 +510,7 @@ namespace NzbDrone.Core.Indexers.Cardigann
                     break;
                 case "date":
                     release.PublishDate = DateTimeUtil.FromUnknown(value);
-                    value = release.PublishDate.ToString(DateTimeUtil.Rfc1123ZPattern);
+                    value = release.PublishDate.ToString(DateTimeUtil.Rfc1123ZPattern, CultureInfo.InvariantCulture);
                     break;
                 case "files":
                     release.Files = ParseUtil.CoerceInt(value);