diff --git a/changelog.md b/changelog.md
index b3ea3a7..b474222 100644
--- a/changelog.md
+++ b/changelog.md
@@ -5,6 +5,7 @@
 - fix gregorianPaschalMoon and gregorianEaster
 - fix negative rollover differences in diffGregorianDurationRollOver and diffJulianDurationRollOver
 - fix case-insensitive parsing for AM/PM markers, UTC, and known timezone names
+- fix timezone offset parsing of malformed minutes and ISO8601 offset ranges
 - fix Unix timezone fallback offset sign and DST abbreviation
 - fix JavaScript getTimeZone offsets and summer flag around DST transitions
 - fix numeric parsers accepting overflowing bounded values
diff --git a/lib/Data/Time/Format/ISO8601.hs b/lib/Data/Time/Format/ISO8601.hs
index 1459b68..093a999 100644
--- a/lib/Data/Time/Format/ISO8601.hs
+++ b/lib/Data/Time/Format/ISO8601.hs
@@ -282,22 +282,28 @@ withUTCDesignator f = f <** specialCaseReadFormat ((), "") (literalFormat "Z")
 timeOffsetFormat :: FormatExtension -> Format TimeZone
 timeOffsetFormat fe =
     let
-        toTimeZone (sign, ehm) =
-            minutesToTimeZone $
-                sign * case ehm of
-                    Left h -> h * 60
-                    Right (h, m) -> h * 60 + m
-        fromTimeZone tz =
+        toOffsetMinutes h m
+            | h < 0 || h > 24 = Nothing
+            | m < 0 || m > 59 = Nothing
+            | h == 24 && m /= 0 = Nothing
+            | otherwise = Just $ h * 60 + m
+        toTimeZone (sign, ehm) = do
+            offset <-
+                case ehm of
+                    Left h -> toOffsetMinutes h 0
+                    Right (h, m) -> toOffsetMinutes h m
+            return $ minutesToTimeZone $ sign * offset
+        fromTimeZone tz = do
             let
                 mm = timeZoneMinutes tz
                 (h, m) = quotRem (abs mm) 60
-            in
-                (signum mm, Right (h, m))
+            _ <- toOffsetMinutes h m
+            return (signum mm, Right (h, m))
         digits2 = integerFormat NoSign (Just 2)
     in
         specialCaseReadFormat (utc, "") $
             specialCaseReadFormat (utc, "Z") $
-                isoMap toTimeZone fromTimeZone $
+                mapMFormat toTimeZone fromTimeZone $
                     mandatorySignFormat <**> (digits2 <++> extColonFormat fe digits2 digits2)
 
 -- | @hh:mm:ss±hh:mm@ (extended), @hhmmss±hhmm@ (basic) [ISO 8601:2004(E) sec. 4.2.5.2]
diff --git a/lib/Data/Time/Format/Parse/Instances.hs b/lib/Data/Time/Format/Parse/Instances.hs
index 53f2ba5..e7b20b5 100644
--- a/lib/Data/Time/Format/Parse/Instances.hs
+++ b/lib/Data/Time/Format/Parse/Instances.hs
@@ -577,7 +577,7 @@ readTzOffset str =
         calc s h1 h2 m1 m2 = do
             sign <- getSign s
             h <- readMaybe [h1, h2]
-            m <- readMaybe [m1, m2]
+            m <- clipValid 0 59 =<< readMaybe [m1, m2]
             return $ sign * (60 * h + m)
     in
         case str of
diff --git a/test/main/Test/Format/ISO8601.hs b/test/main/Test/Format/ISO8601.hs
index 71e4a4c..66316ef 100644
--- a/test/main/Test/Format/ISO8601.hs
+++ b/test/main/Test/Format/ISO8601.hs
@@ -163,6 +163,12 @@ testReadFormat name fmt str val = nameTest (name ++ ": " ++ str) $ assertEqual "
 testReadFormatFails :: (Show t, Eq t) => String -> Format t -> String -> TestTree
 testReadFormatFails name fmt str = nameTest (name ++ ": " ++ str) $ assertEqual "" Nothing $ formatParseM fmt str
 
+testReadFormatFails :: (Show t, Eq t) => String -> Format t -> String -> TestTree
+testReadFormatFails name fmt str = nameTest (name ++ ": " ++ str) $ assertEqual "" Nothing $ formatParseM fmt str
+
+testShowFormatFails :: Show t => String -> Format t -> t -> TestTree
+testShowFormatFails name fmt val = nameTest (name ++ ": " ++ show val) $ assertEqual "" Nothing $ formatShowM fmt val
+
 testShowFormats :: TestTree
 testShowFormats =
     nameTest
@@ -260,6 +266,18 @@ testShowFormats =
         , testReadFormat "timeOffsetFormat" (timeOffsetFormat BasicFormat) "+00" (minutesToTimeZone 0)
         , testReadFormat "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-0000" (minutesToTimeZone 0)
         , testReadFormat "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-00" (minutesToTimeZone 0)
+        , testShowReadFormat "timeOffsetFormat" iso8601Format "+24:00" (minutesToTimeZone 1440)
+        , testReadFormat "timeOffsetFormat" iso8601Format "+24" (minutesToTimeZone 1440)
+        , testShowReadFormat "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-2400" (minutesToTimeZone (-1440))
+        , testReadFormat "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-24" (minutesToTimeZone (-1440))
+        , testReadFormatFails "timeOffsetFormat" (iso8601Format :: Format TimeZone) "+23:60"
+        , testReadFormatFails "timeOffsetFormat" (iso8601Format :: Format TimeZone) "+24:01"
+        , testReadFormatFails "timeOffsetFormat" (iso8601Format :: Format TimeZone) "+25:00"
+        , testReadFormatFails "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-2360"
+        , testReadFormatFails "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-2401"
+        , testReadFormatFails "timeOffsetFormat" (timeOffsetFormat BasicFormat) "-2500"
+        , testShowFormatFails "timeOffsetFormat" (iso8601Format :: Format TimeZone) (minutesToTimeZone 1441)
+        , testShowFormatFails "timeOffsetFormat" (timeOffsetFormat BasicFormat) (minutesToTimeZone (-1441))
         , testShowReadFormat "timeOffsetFormat" iso8601Format "+00:10" (minutesToTimeZone 10)
         , testShowReadFormat "timeOffsetFormat" iso8601Format "-00:10" (minutesToTimeZone (-10))
         , testShowReadFormat "timeOffsetFormat" iso8601Format "+01:35" (minutesToTimeZone 95)
diff --git a/test/main/Test/Format/ParseTime.hs b/test/main/Test/Format/ParseTime.hs
index 2289706..0bdfed8 100644
--- a/test/main/Test/Format/ParseTime.hs
+++ b/test/main/Test/Format/ParseTime.hs
@@ -286,6 +286,8 @@ particularParseTests =
                 ""
                 (Just lowerKnownZone)
                 (parseTimeM False lowerKnownZoneLocale "%Z" "foo")
+        , parseTest False (Just $ TimeZone 1440 False "") "%z" "+2400"
+        , parseTest False (Just $ TimeZone 5940 False "") "%z" "+9900"
         ]
   where
     lowerAmPmLocale = defaultTimeLocale{amPm = ("am", "pm")}
@@ -298,6 +300,10 @@ badParseTests =
         "bad"
         [ parseTest False (Nothing :: Maybe Day) "%Y" ""
         , parseTest False (Nothing :: Maybe TimeOfDay) "%-H" "18446744073709551616"
+        , parseTest False (Nothing :: Maybe TimeZone) "%z" "+2360"
+        , parseTest False (Nothing :: Maybe TimeZone) "%Ez" "+23:60"
+        , parseTest False (Nothing :: Maybe TimeZone) "%Z" "+2360"
+        , parseTest False (Nothing :: Maybe TimeZone) "%EZ" "+23:60"
         ]
 
 {-