From 9d0e4c165a4ecd3270c3ec2bd5184d6d957dba88 Mon Sep 17 00:00:00 2001
From: Alex Gubarev <gubarev.alex@gmail.com>
Date: Wed, 22 Jul 2026 15:54:49 +0300
Subject: [PATCH] Fix Calendar.ISO.parse_time negative zero offsets in basic
 format

---
 lib/elixir/lib/calendar/iso.ex               |  4 ++--
 lib/elixir/test/elixir/calendar/iso_test.exs | 21 +++++++++++++++++---
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/lib/elixir/lib/calendar/iso.ex b/lib/elixir/lib/calendar/iso.ex
index b923fa9475e..241a4ef2f8f 100644
--- a/lib/elixir/lib/calendar/iso.ex
+++ b/lib/elixir/lib/calendar/iso.ex
@@ -2064,7 +2064,6 @@ defmodule Calendar.ISO do
 
   defp parse_offset(""), do: {nil, ""}
   defp parse_offset("Z"), do: {0, ""}
-  defp parse_offset("-00:00"), do: :error
 
   defp parse_offset(<<?+, h1, h2, ?:, m1, m2, rest::binary>>),
     do: parse_offset(1, h1, h2, m1, m2, rest)
@@ -2087,7 +2086,8 @@ defmodule Calendar.ISO do
          true <- m1 in ?0..?5 and m2 in ?0..?9,
          hour = (h1 - ?0) * 10 + h2 - ?0,
          min = (m1 - ?0) * 10 + m2 - ?0,
-         true <- hour < 24 do
+         true <- hour < 24,
+         true <- sign == 1 or hour != 0 or min != 0 do
       {(hour * 60 + min) * 60 * sign, rest}
     else
       _ -> :error
diff --git a/lib/elixir/test/elixir/calendar/iso_test.exs b/lib/elixir/test/elixir/calendar/iso_test.exs
index 91ccb4e760d..454ba23ccfa 100644
--- a/lib/elixir/test/elixir/calendar/iso_test.exs
+++ b/lib/elixir/test/elixir/calendar/iso_test.exs
@@ -154,9 +154,12 @@ defmodule Calendar.ISOTest do
       assert Calendar.ISO.parse_time("23:50:07Z") == {:ok, {23, 50, 7, {0, 0}}}
       assert Calendar.ISO.parse_time("23:50:07+01:00") == {:ok, {23, 50, 7, {0, 0}}}
 
-      assert Calendar.ISO.parse_time("2015-01-23 23:50-00:00") == {:error, :invalid_format}
-      assert Calendar.ISO.parse_time("2015-01-23 23:50-00:60") == {:error, :invalid_format}
-      assert Calendar.ISO.parse_time("2015-01-23 23:50-24:00") == {:error, :invalid_format}
+      assert Calendar.ISO.parse_time("23:50:07-00:00") == {:error, :invalid_format}
+      assert Calendar.ISO.parse_time("23:50:07-0000") == {:error, :invalid_format}
+      assert Calendar.ISO.parse_time("23:50:07-00") == {:error, :invalid_format}
+
+      assert Calendar.ISO.parse_time("23:50:07-00:60") == {:error, :invalid_format}
+      assert Calendar.ISO.parse_time("23:50:07-24:00") == {:error, :invalid_format}
     end
 
     test "supports either comma or period millisecond delimiters" do
@@ -244,6 +247,12 @@ defmodule Calendar.ISOTest do
       assert Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-00:00") ==
                {:error, :invalid_format}
 
+      assert Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-0000") ==
+               {:error, :invalid_format}
+
+      assert Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-00") ==
+               {:error, :invalid_format}
+
       assert Calendar.ISO.parse_naive_datetime("2015-01-23T23:50:07.123-00:60") ==
                {:error, :invalid_format}
 
@@ -321,6 +330,12 @@ defmodule Calendar.ISOTest do
       assert Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.123-00:00") ==
                {:error, :invalid_format}
 
+      assert Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.123-0000") ==
+               {:error, :invalid_format}
+
+      assert Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.123-00") ==
+               {:error, :invalid_format}
+
       assert Calendar.ISO.parse_utc_datetime("2015-01-23T23:50:07.123-00:60") ==
                {:error, :invalid_format}