diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 3c7b3733e..121d622b9 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,5 +1,10 @@
 # Release Notes
 
+## 8.1.2 - Mar 17 2026
+
+- Fix `TextConversions.AsDateTime` and `TextConversions.AsDateTimeOffset` to return `None` (instead of throwing `ArgumentOutOfRangeException`) when a `/Date(...)/` value overflows the valid `DateTime`/`DateTimeOffset` range; use `InvariantCulture` explicitly when parsing the milliseconds value
+- Fix error message in Range header validation: show the original header value (not the internal byte array representation) when the range format is invalid
+
 ## 8.1.1 - Mar 14 2026
 
 - Fix `CombinedStream` to throw `NotSupportedException` (instead of `Exception`) for unsupported operations (write, seek, set length); fixes a typo in the length error message
diff --git a/src/FSharp.Data.Http/Http.fs b/src/FSharp.Data.Http/Http.fs
index 52c67d53c..10056cbaf 100644
--- a/src/FSharp.Data.Http/Http.fs
+++ b/src/FSharp.Data.Http/Http.fs
@@ -1745,7 +1745,7 @@ module internal HttpHelpers =
                 let bytes = value.Substring("bytes=".Length).Split('-')
 
                 if bytes.Length <> 2 then
-                    failwithf "Invalid value for the Range header (%O)" bytes
+                    failwithf "Invalid value for the Range header (%s)" value
 
                 req.AddRange(int64 bytes.[0], int64 bytes.[1])
             | "proxy-authorization" -> req.Headers.[HeaderEnum.ProxyAuthorization] <- value
diff --git a/src/FSharp.Data.Runtime.Utilities/TextConversions.fs b/src/FSharp.Data.Runtime.Utilities/TextConversions.fs
index 0226a0cce..2170532f3 100644
--- a/src/FSharp.Data.Runtime.Utilities/TextConversions.fs
+++ b/src/FSharp.Data.Runtime.Utilities/TextConversions.fs
@@ -171,10 +171,19 @@ type TextConversions private () =
         let matchesMS = msDateRegex.Value.Match(text.Trim())
 
         if matchesMS.Success then
-            matchesMS.Groups.[1].Value
-            |> Double.Parse
-            |> DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddMilliseconds
-            |> Some
+            match
+                Double.TryParse(
+                    matchesMS.Groups.[1].Value,
+                    Globalization.NumberStyles.Integer,
+                    Globalization.CultureInfo.InvariantCulture
+                )
+            with
+            | true, ms when not (Double.IsInfinity ms) ->
+                try
+                    DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddMilliseconds ms |> Some
+                with :? ArgumentOutOfRangeException ->
+                    None
+            | _ -> None
         else
             // Parse ISO 8601 format, fixing time zone if needed
             match ParseISO8601FormattedDateTime text cultureInfo with
@@ -208,10 +217,19 @@ type TextConversions private () =
             // e.g. 1231456+1000, 123123+0000, 123123-0500, etc.
             match offset matchesMS.Groups.[2].Value with
             | ValueSome ofst ->
-                matchesMS.Groups.[1].Value
-                |> Double.Parse
-                |> DateTimeOffset(1970, 1, 1, 0, 0, 0, ofst).AddMilliseconds
-                |> Some
+                match
+                    Double.TryParse(
+                        matchesMS.Groups.[1].Value,
+                        Globalization.NumberStyles.Integer,
+                        Globalization.CultureInfo.InvariantCulture
+                    )
+                with
+                | true, ms when not (Double.IsInfinity ms) ->
+                    try
+                        DateTimeOffset(1970, 1, 1, 0, 0, 0, ofst).AddMilliseconds ms |> Some
+                    with :? ArgumentOutOfRangeException ->
+                        None
+                | _ -> None
             | ValueNone -> None
         else
             match ParseISO8601FormattedDateTime text cultureInfo with
diff --git a/tests/FSharp.Data.Core.Tests/TextConversions.fs b/tests/FSharp.Data.Core.Tests/TextConversions.fs
index 8ae3d0041..4e34501cf 100644
--- a/tests/FSharp.Data.Core.Tests/TextConversions.fs
+++ b/tests/FSharp.Data.Core.Tests/TextConversions.fs
@@ -163,6 +163,10 @@ let ``DateTime conversions with various formats``() =
   TextConversions.AsDateTime culture "/Date(1577836800000)/" |> Option.isSome |> should equal true
   TextConversions.AsDateTime culture "/Date(1577836800000+0000)/" |> Option.isSome |> should equal true
   
+  // Overflow-safe: astronomically large ms-Date values should return None rather than throwing
+  TextConversions.AsDateTime culture ("/Date(" + System.String('9', 500) + ")/") |> should equal None
+  TextConversions.AsDateTime culture ("/Date(-" + System.String('9', 500) + ")/") |> should equal None
+  
   // Invalid values
   TextConversions.AsDateTime culture "not-a-date" |> should equal None
   TextConversions.AsDateTime culture "" |> should equal None
@@ -190,6 +194,9 @@ let ``DateTimeOffset conversions with additional formats``() =
   TextConversions.AsDateTimeOffset culture "2020-01-01T12:00:00+05:30" |> Option.isSome |> should equal true
   TextConversions.AsDateTimeOffset culture "2020-01-01T12:00:00-08:00" |> Option.isSome |> should equal true
   
+  // Overflow-safe: astronomically large ms-Date+offset values should return None rather than throwing
+  TextConversions.AsDateTimeOffset culture ("/Date(" + System.String('9', 500) + "+0000)/") |> should equal None
+  
   // Invalid values
   TextConversions.AsDateTimeOffset culture "2020-01-01" |> should equal None
   TextConversions.AsDateTimeOffset culture "invalid" |> should equal None