From c856b2142cbab7c1f3fc2bb5c360186e165bf2b5 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sun, 1 Feb 2026 11:56:04 -0600
Subject: [PATCH] Add timezone validation to reject invalid IANA timezone
 strings

Prevents invalid timezone values from being stored in the database
by validating against Elixir's time zone database during registration.
---
 config/config.exs               |  3 +++
 lib/towerops/accounts/user.ex   | 19 +++++++++++++++++++
 mix.exs                         |  1 +
 mix.lock                        |  7 +++++++
 test/towerops/accounts_test.exs | 14 ++++++++++++++
 5 files changed, 44 insertions(+)

diff --git a/config/config.exs b/config/config.exs
index d4a92d0f..a850f459 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -7,6 +7,9 @@
 # General application configuration
 import Config
 
+# Configure time zone database to use tzdata for IANA timezone support
+config :elixir, :time_zone_database, Tzdata.TimeZoneDatabase
+
 # Configure esbuild (the version is required)
 config :esbuild,
   version: "0.25.4",
diff --git a/lib/towerops/accounts/user.ex b/lib/towerops/accounts/user.ex
index 7d3341e8..f28e21f8 100644
--- a/lib/towerops/accounts/user.ex
+++ b/lib/towerops/accounts/user.ex
@@ -126,6 +126,7 @@ defmodule Towerops.Accounts.User do
     |> validate_email_for_registration(opts)
     |> validate_password(opts)
     |> validate_consent()
+    |> validate_timezone()
   end
 
   defp validate_consent(changeset) do
@@ -138,6 +139,24 @@ defmodule Towerops.Accounts.User do
     )
   end
 
+  defp validate_timezone(changeset) do
+    validate_change(changeset, :timezone, fn :timezone, timezone ->
+      validate_timezone_value(timezone)
+    end)
+  end
+
+  defp validate_timezone_value(timezone) when is_nil(timezone) or timezone == "", do: []
+
+  defp validate_timezone_value(timezone) do
+    # Validate by attempting to shift a datetime to the given timezone
+    # This works with Calendar.UTCOnlyTimeZoneDatabase which only accepts "Etc/UTC" and "UTC"
+    # For full IANA timezone support, tzdata package would be needed
+    case DateTime.shift_zone(DateTime.utc_now(), timezone) do
+      {:ok, _} -> []
+      {:error, _} -> [timezone: "is not a valid timezone"]
+    end
+  end
+
   defp validate_email_for_registration(changeset, opts) do
     changeset =
       changeset
diff --git a/mix.exs b/mix.exs
index bda04c83..fd5de870 100644
--- a/mix.exs
+++ b/mix.exs
@@ -79,6 +79,7 @@ defmodule Towerops.MixProject do
       {:mox, "~> 1.0", only: :test},
       {:honeybadger, "~> 0.24"},
       {:stream_data, "~> 1.1", only: :test},
+      {:tzdata, "~> 1.1"},
       {:styler, "~> 1.10", only: [:dev, :test], runtime: false},
       {:mix_test_watch, "~> 1.0", only: [:dev, :test], runtime: false},
       {:dialyxir, "~> 1.4", only: [:dev, :test], runtime: false},
diff --git a/mix.lock b/mix.lock
index 7980c4dc..d00f15d8 100644
--- a/mix.lock
+++ b/mix.lock
@@ -4,6 +4,7 @@
   "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},
   "cbor": {:hex, :cbor, "1.0.1", "39511158e8ea5a57c1fcb9639aaa7efde67129678fee49ebbda780f6f24959b0", [:mix], [], "hexpm", "5431acbe7a7908f17f6a9cd43311002836a34a8ab01876918d8cfb709cd8b6a2"},
   "cc_precompiler": {:hex, :cc_precompiler, "0.1.11", "8c844d0b9fb98a3edea067f94f616b3f6b29b959b6b3bf25fee94ffe34364768", [:mix], [{:elixir_make, "~> 0.7", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm", "3427232caf0835f94680e5bcf082408a70b48ad68a5f5c0b02a3bea9f3a075b9"},
+  "certifi": {:hex, :certifi, "2.15.0", "0e6e882fcdaaa0a5a9f2b3db55b1394dba07e8d6d9bcad08318fb604c6839712", [:rebar3], [], "hexpm", "b147ed22ce71d72eafdad94f055165c1c182f61a2ff49df28bcc71d1d5b94a60"},
   "comeonin": {:hex, :comeonin, "5.5.1", "5113e5f3800799787de08a6e0db307133850e635d34e9fab23c70b6501669510", [:mix], [], "hexpm", "65aac8f19938145377cee73973f192c5645873dcf550a8a6b18187d17c13ccdb"},
   "credo": {:hex, :credo, "1.7.16", "a9f1389d13d19c631cb123c77a813dbf16449a2aebf602f590defa08953309d4", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "d0562af33756b21f248f066a9119e3890722031b6d199f22e3cf95550e4f1579"},
   "db_connection": {:hex, :db_connection, "2.9.0", "a6a97c5c958a2d7091a58a9be40caf41ab496b0701d21e1d1abff3fa27a7f371", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "17d502eacaf61829db98facf6f20808ed33da6ccf495354a41e64fe42f9c509c"},
@@ -23,6 +24,7 @@
   "fine": {:hex, :fine, "0.1.4", "b19a89c1476c7c57afb5f9314aed5960b5bc95d5277de4cb5ee8e1d1616ce379", [:mix], [], "hexpm", "be3324cc454a42d80951cf6023b9954e9ff27c6daa255483b3e8d608670303f5"},
   "gen_smtp": {:hex, :gen_smtp, "1.3.0", "62c3d91f0dcf6ce9db71bcb6881d7ad0d1d834c7f38c13fa8e952f4104a8442e", [:rebar3], [{:ranch, ">= 1.8.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "0b73fbf069864ecbce02fe653b16d3f35fd889d0fdd4e14527675565c39d84e6"},
   "gettext": {:hex, :gettext, "1.0.2", "5457e1fd3f4abe47b0e13ff85086aabae760497a3497909b8473e0acee57673b", [:mix], [{:expo, "~> 0.5.1 or ~> 1.0", [hex: :expo, repo: "hexpm", optional: false]}], "hexpm", "eab805501886802071ad290714515c8c4a17196ea76e5afc9d06ca85fb1bfeb3"},
+  "hackney": {:hex, :hackney, "1.25.0", "390e9b83f31e5b325b9f43b76e1a785cbdb69b5b6cd4e079aa67835ded046867", [:rebar3], [{:certifi, "~> 2.15.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~> 6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~> 1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~> 1.4", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.4.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~> 1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~> 0.7.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "7209bfd75fd1f42467211ff8f59ea74d6f2a9e81cbcee95a56711ee79fd6b1d4"},
   "heroicons": {:git, "https://github.com/tailwindlabs/heroicons.git", "0435d4ca364a608cc75e2f8683d374e55abbae26", [tag: "v2.2.0", sparse: "optimized", depth: 1]},
   "honeybadger": {:hex, :honeybadger, "0.24.1", "13ffe56b4d148649c8fbb0e091fefecc5d8e8eb7ade684b6900085a947d741d5", [:mix], [{:ecto, ">= 2.0.0", [hex: :ecto, repo: "hexpm", optional: true]}, {:hackney, "~> 1.1", [hex: :hackney, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:phoenix, ">= 1.0.0 and < 2.0.0", [hex: :phoenix, repo: "hexpm", optional: true]}, {:plug, ">= 1.0.0 and < 2.0.0", [hex: :plug, repo: "hexpm", optional: true]}, {:process_tree, "~> 0.2.1", [hex: :process_tree, repo: "hexpm", optional: false]}, {:req, "~> 0.5.0", [hex: :req, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "0c97d5a82c42298b9935dbc0a7e3c14372c8f55257f603828258ef9f7e0da892"},
   "hpax": {:hex, :hpax, "1.0.3", "ed67ef51ad4df91e75cc6a1494f851850c0bd98ebc0be6e81b026e765ee535aa", [:mix], [], "hexpm", "8eab6e1cfa8d5918c2ce4ba43588e894af35dbd8e91e6e55c817bca5847df34a"},
@@ -30,7 +32,9 @@
   "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
   "lazy_html": {:hex, :lazy_html, "0.1.8", "677a8642e644eef8de98f3040e2520d42d0f0f8bd6c5cd49db36504e34dffe91", [:make, :mix], [{:cc_precompiler, "~> 0.1", [hex: :cc_precompiler, repo: "hexpm", optional: false]}, {:elixir_make, "~> 0.9.0", [hex: :elixir_make, repo: "hexpm", optional: false]}, {:fine, "~> 0.1.0", [hex: :fine, repo: "hexpm", optional: false]}], "hexpm", "0d8167d930b704feb94b41414ca7f5779dff9bca7fcf619fcef18de138f08736"},
   "libcluster": {:hex, :libcluster, "3.5.0", "5ee4cfde4bdf32b2fef271e33ce3241e89509f4344f6c6a8d4069937484866ba", [:mix], [{:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.3", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "ebf6561fcedd765a4cd43b4b8c04b1c87f4177b5fb3cbdfe40a780499d72f743"},
+  "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm", "69b09adddc4f74a40716ae54d140f93beb0fb8978d8636eaded0c31b6f099f16"},
   "mime": {:hex, :mime, "2.0.7", "b8d739037be7cd402aee1ba0306edfdef982687ee7e9859bee6198c1e7e2f128", [:mix], [], "hexpm", "6171188e399ee16023ffc5b76ce445eb6d9672e2e241d2df6050f3c771e80ccd"},
+  "mimerl": {:hex, :mimerl, "1.4.0", "3882a5ca67fbbe7117ba8947f27643557adec38fa2307490c4c4207624cb213b", [:rebar3], [], "hexpm", "13af15f9f68c65884ecca3a3891d50a7b57d82152792f3e19d88650aa126b144"},
   "mint": {:hex, :mint, "1.7.1", "113fdb2b2f3b59e47c7955971854641c61f378549d73e829e1768de90fc1abf1", [:mix], [{:castore, "~> 0.1.0 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:hpax, "~> 0.1.1 or ~> 0.2.0 or ~> 1.0", [hex: :hpax, repo: "hexpm", optional: false]}], "hexpm", "fceba0a4d0f24301ddee3024ae116df1c3f4bb7a563a731f45fdfeb9d39a231b"},
   "mix_audit": {:hex, :mix_audit, "2.1.5", "c0f77cee6b4ef9d97e37772359a187a166c7a1e0e08b50edf5bf6959dfe5a016", [:make, :mix], [{:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: false]}, {:yaml_elixir, "~> 2.11", [hex: :yaml_elixir, repo: "hexpm", optional: false]}], "hexpm", "87f9298e21da32f697af535475860dc1d3617a010e0b418d2ec6142bc8b42d69"},
   "mix_test_watch": {:hex, :mix_test_watch, "1.4.0", "d88bcc4fbe3198871266e9d2f00cd8ae350938efbb11d3fa1da091586345adbb", [:mix], [{:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm", "2b4693e17c8ead2ef56d4f48a0329891e8c2d0d73752c0f09272a2b17dc38d1b"},
@@ -42,6 +46,7 @@
   "oban": {:hex, :oban, "2.20.3", "e4d27336941955886cc7113420c32c63b70b64f10b27e08e3cf2b001153953cd", [:mix], [{:ecto_sql, "~> 3.10", [hex: :ecto_sql, repo: "hexpm", optional: false]}, {:ecto_sqlite3, "~> 0.9", [hex: :ecto_sqlite3, repo: "hexpm", optional: true]}, {:igniter, "~> 0.5", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: true]}, {:myxql, "~> 0.7", [hex: :myxql, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.20", [hex: :postgrex, repo: "hexpm", optional: true]}, {:telemetry, "~> 1.3", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "075ffbf1279a96bec495bc63d647b08929837d70bcc0427249ffe4d1dddaec33"},
   "oban_met": {:hex, :oban_met, "1.0.5", "bb633ab06448dab2ef9194f6688d33b3d07fc3f2ad793a1a08f4dfbb2cc9fe50", [:mix], [{:oban, "~> 2.19", [hex: :oban, repo: "hexpm", optional: false]}], "hexpm", "64664d50805bbfd3903aeada1f3c39634652a87844797ee400b0bcc95a28f5ea"},
   "oban_web": {:hex, :oban_web, "2.11.7", "a998868bb32b3d3c44f328a8baec820af5c3b46a3a743d89c169e75b0bf7efcc", [:mix], [{:jason, "~> 1.2", [hex: :jason, repo: "hexpm", optional: false]}, {:oban, "~> 2.19", [hex: :oban, repo: "hexpm", optional: false]}, {:oban_met, "~> 1.0", [hex: :oban_met, repo: "hexpm", optional: false]}, {:phoenix, "~> 1.7", [hex: :phoenix, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 3.3 or ~> 4.0", [hex: :phoenix_html, repo: "hexpm", optional: false]}, {:phoenix_live_view, "~> 1.0", [hex: :phoenix_live_view, repo: "hexpm", optional: false]}, {:phoenix_pubsub, "~> 2.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}], "hexpm", "f0ef9ec8f97381a0287c60a732736ff77bc351cbbe82eceffb5a635f84788656"},
+  "parse_trans": {:hex, :parse_trans, "3.4.1", "6e6aa8167cb44cc8f39441d05193be6e6f4e7c2946cb2759f015f8c56b76e5ff", [:rebar3], [], "hexpm", "620a406ce75dada827b82e453c19cf06776be266f5a67cff34e1ef2cbb60e49a"},
   "phoenix": {:hex, :phoenix, "1.8.3", "49ac5e485083cb1495a905e47eb554277bdd9c65ccb4fc5100306b350151aa95", [:mix], [{:bandit, "~> 1.0", [hex: :bandit, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 2.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:phoenix_template, "~> 1.0", [hex: :phoenix_template, repo: "hexpm", optional: false]}, {:phoenix_view, "~> 2.0", [hex: :phoenix_view, repo: "hexpm", optional: true]}, {:plug, "~> 1.14", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.7", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:plug_crypto, "~> 1.2 or ~> 2.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}, {:websock_adapter, "~> 0.5.3", [hex: :websock_adapter, repo: "hexpm", optional: false]}], "hexpm", "36169f95cc2e155b78be93d9590acc3f462f1e5438db06e6248613f27c80caec"},
   "phoenix_ecto": {:hex, :phoenix_ecto, "4.7.0", "75c4b9dfb3efdc42aec2bd5f8bccd978aca0651dbcbc7a3f362ea5d9d43153c6", [:mix], [{:ecto, "~> 3.5", [hex: :ecto, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 2.14.2 or ~> 3.0 or ~> 4.1", [hex: :phoenix_html, repo: "hexpm", optional: true]}, {:plug, "~> 1.9", [hex: :plug, repo: "hexpm", optional: false]}, {:postgrex, "~> 0.16 or ~> 1.0", [hex: :postgrex, repo: "hexpm", optional: true]}], "hexpm", "1d75011e4254cb4ddf823e81823a9629559a1be93b4321a6a5f11a5306fbf4cc"},
   "phoenix_html": {:hex, :phoenix_html, "4.3.0", "d3577a5df4b6954cd7890c84d955c470b5310bb49647f0a114a6eeecc850f7ad", [:mix], [], "hexpm", "3eaa290a78bab0f075f791a46a981bbe769d94bc776869f4f3063a14f30497ad"},
@@ -61,6 +66,7 @@
   "redix": {:hex, :redix, "1.5.3", "4eaae29c75e3285c0ff9957046b7c209aa7f72a023a17f0a9ea51c2a50ab5b0f", [:mix], [{:castore, "~> 0.1.0 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:nimble_options, "~> 0.5.0 or ~> 1.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.0 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "7b06fb5246373af41f5826b03334dfa3f636347d4d5d98b4d455b699d425ae7e"},
   "req": {:hex, :req, "0.5.17", "0096ddd5b0ed6f576a03dde4b158a0c727215b15d2795e59e0916c6971066ede", [:mix], [{:brotli, "~> 0.3.1", [hex: :brotli, repo: "hexpm", optional: true]}, {:ezstd, "~> 1.0", [hex: :ezstd, repo: "hexpm", optional: true]}, {:finch, "~> 0.17", [hex: :finch, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}, {:mime, "~> 2.0.6 or ~> 2.1", [hex: :mime, repo: "hexpm", optional: false]}, {:nimble_csv, "~> 1.0", [hex: :nimble_csv, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: true]}], "hexpm", "0b8bc6ffdfebbc07968e59d3ff96d52f2202d0536f10fef4dc11dc02a2a43e39"},
   "sobelow": {:hex, :sobelow, "0.14.1", "2f81e8632f15574cba2402bcddff5497b413c01e6f094bc0ab94e83c2f74db81", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "8fac9a2bd90fdc4b15d6fca6e1608efb7f7c600fa75800813b794ee9364c87f2"},
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.7", "354c321cf377240c7b8716899e182ce4890c5938111a1296add3ec74cf1715df", [:make, :mix, :rebar3], [], "hexpm", "fe4c190e8f37401d30167c8c405eda19469f34577987c76dde613e838bbc67f8"},
   "stream_data": {:hex, :stream_data, "1.2.0", "58dd3f9e88afe27dc38bef26fce0c84a9e7a96772b2925c7b32cd2435697a52b", [:mix], [], "hexpm", "eb5c546ee3466920314643edf68943a5b14b32d1da9fe01698dc92b73f89a9ed"},
   "styler": {:hex, :styler, "1.10.1", "9229050c978bfaaab1d94e8673843576d0127d48fe64824a30babde3d6342475", [:mix], [], "hexpm", "d86cbcc70e8ab424393af313d1d885931ba9dc7c383d7dd30f4ab255a8d39f73"},
   "sweet_xml": {:hex, :sweet_xml, "0.7.5", "803a563113981aaac202a1dbd39771562d0ad31004ddbfc9b5090bdcd5605277", [:mix], [], "hexpm", "193b28a9b12891cae351d81a0cead165ffe67df1b73fe5866d10629f4faefb12"},
@@ -71,6 +77,7 @@
   "telemetry_metrics": {:hex, :telemetry_metrics, "1.1.0", "5bd5f3b5637e0abea0426b947e3ce5dd304f8b3bc6617039e2b5a008adc02f8f", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "e7b79e8ddfde70adb6db8a6623d1778ec66401f366e9a8f5dd0955c56bc8ce67"},
   "telemetry_poller": {:hex, :telemetry_poller, "1.3.0", "d5c46420126b5ac2d72bc6580fb4f537d35e851cc0f8dbd571acf6d6e10f5ec7", [:rebar3], [{:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "51f18bed7128544a50f75897db9974436ea9bfba560420b646af27a9a9b35211"},
   "thousand_island": {:hex, :thousand_island, "1.4.3", "2158209580f633be38d43ec4e3ce0a01079592b9657afff9080d5d8ca149a3af", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "6e4ce09b0fd761a58594d02814d40f77daff460c48a7354a15ab353bb998ea0b"},
+  "tzdata": {:hex, :tzdata, "1.1.3", "b1cef7bb6de1de90d4ddc25d33892b32830f907e7fc2fccd1e7e22778ab7dfbc", [:mix], [{:hackney, "~> 1.17", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "d4ca85575a064d29d4e94253ee95912edfb165938743dbf002acdf0dcecb0c28"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.7.1", "a48703a25c170eedadca83b11e88985af08d35f37c6f664d6dcfb106a97782fc", [:rebar3], [], "hexpm", "b3a917854ce3ae233619744ad1e0102e05673136776fb2fa76234f3e03b23642"},
   "websock": {:hex, :websock, "0.5.3", "2f69a6ebe810328555b6fe5c831a851f485e303a7c8ce6c5f675abeb20ebdadc", [:mix], [], "hexpm", "6105453d7fac22c712ad66fab1d45abdf049868f253cf719b625151460b8b453"},
   "websock_adapter": {:hex, :websock_adapter, "0.5.9", "43dc3ba6d89ef5dec5b1d0a39698436a1e856d000d84bf31a3149862b01a287f", [:mix], [{:bandit, ">= 0.6.0", [hex: :bandit, repo: "hexpm", optional: true]}, {:plug, "~> 1.14", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.6", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:websock, "~> 0.5", [hex: :websock, repo: "hexpm", optional: false]}], "hexpm", "5534d5c9adad3c18a0f58a9371220d75a803bf0b9a3d87e6fe072faaeed76a08"},
diff --git a/test/towerops/accounts_test.exs b/test/towerops/accounts_test.exs
index 84e576a5..148e389b 100644
--- a/test/towerops/accounts_test.exs
+++ b/test/towerops/accounts_test.exs
@@ -800,5 +800,19 @@ defmodule Towerops.AccountsTest do
       assert {:ok, user} = Accounts.register_user_with_organization(valid_attrs)
       assert user.timezone == "UTC"
     end
+
+    test "rejects invalid timezone format" do
+      valid_attrs = %{
+        "email" => "invalid-tz@example.com",
+        "password" => "a valid password",
+        "privacy_policy_consent" => true,
+        "terms_of_service_consent" => true,
+        "organization_name" => "Test Org",
+        "timezone" => "Not/A/Real/Timezone"
+      }
+
+      assert {:error, changeset} = Accounts.register_user_with_organization(valid_attrs)
+      assert "is not a valid timezone" in errors_on(changeset).timezone
+    end
   end
 end