diff --git a/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Reader/CborReader.Tag.cs b/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Reader/CborReader.Tag.cs
index 238217856c1905..2dd4c4d1d9abe1 100644
--- a/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Reader/CborReader.Tag.cs
+++ b/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Reader/CborReader.Tag.cs
@@ -72,7 +72,7 @@ public DateTimeOffset ReadDateTimeOffset()
                 string dateString = ReadTextString();
 
                 // TODO determine if conformance modes should allow inexact date sting parsing
-                if (!DateTimeOffset.TryParseExact(dateString, CborWriter.Rfc3339FormatString, null, DateTimeStyles.RoundtripKind, out DateTimeOffset result))
+                if (!DateTimeOffset.TryParseExact(dateString, CborWriter.Rfc3339FormatString, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out DateTimeOffset result))
                 {
                     throw new CborContentException(SR.Cbor_Reader_InvalidDateTimeEncoding);
                 }
diff --git a/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Writer/CborWriter.Tag.cs b/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Writer/CborWriter.Tag.cs
index e5e772dcfd1be5..3ca04f085e04c0 100644
--- a/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Writer/CborWriter.Tag.cs
+++ b/src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/Writer/CborWriter.Tag.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
+using System.Globalization;
 using System.Numerics;
 
 namespace System.Formats.Cbor
@@ -42,8 +43,8 @@ public void WriteDateTimeOffset(DateTimeOffset value)
 #else
                 value.Offset == TimeSpan.Zero ?
 #endif // NET8_0_OR_GREATER
-                value.UtcDateTime.ToString(Rfc3339FormatString) : // prefer 'Z' over '+00:00'
-                value.ToString(Rfc3339FormatString);
+                value.UtcDateTime.ToString(Rfc3339FormatString, CultureInfo.InvariantCulture) : // prefer 'Z' over '+00:00'
+                value.ToString(Rfc3339FormatString, CultureInfo.InvariantCulture);
 
             WriteTag(CborTag.DateTimeString);
             WriteTextString(dateString);