From 5d7e12b72de90d139b91359406a4849680b993c0 Mon Sep 17 00:00:00 2001
From: Christian Schmidt <github@chsc.dk>
Date: Thu, 12 Sep 2024 17:18:40 +0200
Subject: [PATCH] Move time zone logic into mailers

---
 app/mailers/admin_mailer.rb                   | 15 +++---
 app/mailers/application_mailer.rb             |  6 ++-
 app/mailers/notification_mailer.rb            | 10 ++--
 app/mailers/user_mailer.rb                    | 48 ++++++++++---------
 .../notification_mailer/_status.html.haml     |  2 +-
 .../user_mailer/appeal_approved.html.haml     |  4 +-
 .../user_mailer/appeal_approved.text.erb      |  2 +-
 .../user_mailer/appeal_rejected.html.haml     |  4 +-
 .../user_mailer/appeal_rejected.text.erb      |  2 +-
 app/views/user_mailer/failed_2fa.html.haml    |  2 +-
 app/views/user_mailer/failed_2fa.text.erb     |  2 +-
 .../user_mailer/suspicious_sign_in.html.haml  |  2 +-
 .../user_mailer/suspicious_sign_in.text.erb   |  2 +-
 config/application.rb                         |  3 +-
 config/initializers/time_zone.rb              |  4 ++
 spec/mailers/notification_mailer_spec.rb      |  7 ++-
 spec/mailers/user_mailer_spec.rb              | 32 +++++--------
 spec/support/examples/mailers.rb              | 27 +++++++++++
 18 files changed, 102 insertions(+), 72 deletions(-)
 create mode 100644 config/initializers/time_zone.rb

diff --git a/app/mailers/admin_mailer.rb b/app/mailers/admin_mailer.rb
index 8dd7b6e59f..7df546ef5f 100644
--- a/app/mailers/admin_mailer.rb
+++ b/app/mailers/admin_mailer.rb
@@ -14,7 +14,7 @@ class AdminMailer < ApplicationMailer
   def new_report(report)
     @report = report
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance, id: @report.id)
     end
   end
@@ -22,7 +22,7 @@ class AdminMailer < ApplicationMailer
   def new_appeal(appeal)
     @appeal = appeal
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance, username: @appeal.account.username)
     end
   end
@@ -30,7 +30,7 @@ class AdminMailer < ApplicationMailer
   def new_pending_account(user)
     @account = user.account
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance, username: @account.username)
     end
   end
@@ -40,7 +40,7 @@ class AdminMailer < ApplicationMailer
     @tags                   = tags
     @statuses               = statuses
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance)
     end
   end
@@ -48,7 +48,7 @@ class AdminMailer < ApplicationMailer
   def new_software_updates
     @software_updates = SoftwareUpdate.all.to_a.sort_by(&:gem_version)
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance)
     end
   end
@@ -60,13 +60,13 @@ class AdminMailer < ApplicationMailer
     headers['X-Priority'] = '1'
     headers['Importance'] = 'high'
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance)
     end
   end
 
   def auto_close_registrations
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(instance: @instance)
     end
   end
@@ -75,6 +75,7 @@ class AdminMailer < ApplicationMailer
 
   def process_params
     @me = params[:recipient]
+    @user = @me.user
   end
 
   def set_instance
diff --git a/app/mailers/application_mailer.rb b/app/mailers/application_mailer.rb
index 35f0b5fee1..ba3009cda7 100644
--- a/app/mailers/application_mailer.rb
+++ b/app/mailers/application_mailer.rb
@@ -11,8 +11,10 @@ class ApplicationMailer < ActionMailer::Base
 
   protected
 
-  def locale_for_account(account, &block)
-    I18n.with_locale(account.user_locale || I18n.default_locale, &block)
+  def with_user(user, &block)
+    I18n.with_locale(user.locale || I18n.default_locale) do
+      Time.use_zone(user.time_zone || ENV['DEFAULT_TIME_ZONE'] || 'UTC', &block)
+    end
   end
 
   def set_autoreply_headers!
diff --git a/app/mailers/notification_mailer.rb b/app/mailers/notification_mailer.rb
index 4eb38ec340..a9050210be 100644
--- a/app/mailers/notification_mailer.rb
+++ b/app/mailers/notification_mailer.rb
@@ -17,7 +17,7 @@ class NotificationMailer < ApplicationMailer
   def mention
     return unless @user.functional? && @status.present?
 
-    locale_for_account(@me) do
+    with_user(@user) do
       thread_by_conversation(@status.conversation)
       mail subject: default_i18n_subject(name: @status.account.acct)
     end
@@ -26,7 +26,7 @@ class NotificationMailer < ApplicationMailer
   def follow
     return unless @user.functional?
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(name: @account.acct)
     end
   end
@@ -34,7 +34,7 @@ class NotificationMailer < ApplicationMailer
   def favourite
     return unless @user.functional? && @status.present?
 
-    locale_for_account(@me) do
+    with_user(@user) do
       thread_by_conversation(@status.conversation)
       mail subject: default_i18n_subject(name: @account.acct)
     end
@@ -43,7 +43,7 @@ class NotificationMailer < ApplicationMailer
   def reblog
     return unless @user.functional? && @status.present?
 
-    locale_for_account(@me) do
+    with_user(@user) do
       thread_by_conversation(@status.conversation)
       mail subject: default_i18n_subject(name: @account.acct)
     end
@@ -52,7 +52,7 @@ class NotificationMailer < ApplicationMailer
   def follow_request
     return unless @user.functional?
 
-    locale_for_account(@me) do
+    with_user(@user) do
       mail subject: default_i18n_subject(name: @account.acct)
     end
   end
diff --git a/app/mailers/user_mailer.rb b/app/mailers/user_mailer.rb
index 5c9e5c96d9..e81fee7b9e 100644
--- a/app/mailers/user_mailer.rb
+++ b/app/mailers/user_mailer.rb
@@ -20,7 +20,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
       mail to: @resource.unconfirmed_email.presence || @resource.email,
            subject: I18n.t(@resource.pending_reconfirmation? ? 'devise.mailer.reconfirmation_instructions.subject' : 'devise.mailer.confirmation_instructions.subject', instance: @instance),
            template_name: @resource.pending_reconfirmation? ? 'reconfirmation_instructions' : 'confirmation_instructions'
@@ -33,7 +33,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -43,7 +43,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -53,7 +53,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -63,7 +63,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -73,7 +73,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -83,7 +83,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -93,7 +93,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -103,7 +103,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: default_devise_subject
     end
   end
@@ -114,7 +114,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: I18n.t('devise.mailer.webauthn_credential.added.subject')
     end
   end
@@ -125,7 +125,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale(use_current_locale: true)) do
+    with_user(@resource, use_current_locale: true) do
       mail subject: I18n.t('devise.mailer.webauthn_credential.deleted.subject')
     end
   end
@@ -141,7 +141,7 @@ class UserMailer < Devise::Mailer
     @has_active_relationships = @resource.account.active_relationships.exists?
     @has_statuses = @resource.account.statuses.exists?
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
       mail subject: default_i18n_subject
     end
   end
@@ -152,7 +152,7 @@ class UserMailer < Devise::Mailer
 
     return unless @resource.active_for_authentication?
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
       mail subject: default_i18n_subject
     end
   end
@@ -162,7 +162,7 @@ class UserMailer < Devise::Mailer
     @warning  = warning
     @statuses = @warning.statuses.includes(:account, :preloadable_poll, :media_attachments, active_mentions: [:account])
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
       mail subject: I18n.t("user_mailer.warning.subject.#{@warning.action}", acct: "@#{user.account.local_username_and_domain}")
     end
   end
@@ -171,7 +171,7 @@ class UserMailer < Devise::Mailer
     @resource = user
     @appeal   = appeal
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
       mail subject: default_i18n_subject(date: l(@appeal.created_at))
     end
   end
@@ -180,7 +180,7 @@ class UserMailer < Devise::Mailer
     @resource = user
     @appeal   = appeal
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
       mail subject: default_i18n_subject(date: l(@appeal.created_at))
     end
   end
@@ -190,9 +190,10 @@ class UserMailer < Devise::Mailer
     @remote_ip  = remote_ip
     @user_agent = user_agent
     @detection  = Browser.new(user_agent)
-    @timestamp  = timestamp.to_time.utc
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
+      @timestamp = timestamp.in_time_zone
+
       mail subject: default_i18n_subject
     end
   end
@@ -202,9 +203,10 @@ class UserMailer < Devise::Mailer
     @remote_ip  = remote_ip
     @user_agent = user_agent
     @detection  = Browser.new(user_agent)
-    @timestamp  = timestamp.to_time.utc
 
-    I18n.with_locale(locale) do
+    with_user(@resource) do
+      @timestamp = timestamp.in_time_zone
+
       mail subject: default_i18n_subject
     end
   end
@@ -219,7 +221,9 @@ class UserMailer < Devise::Mailer
     @instance = Rails.configuration.x.local_domain
   end
 
-  def locale(use_current_locale: false)
-    @resource.locale.presence || (use_current_locale && I18n.locale) || I18n.default_locale
+  def with_user(user, use_current_locale: false, &block)
+    I18n.with_locale(user.locale || (use_current_locale && I18n.locale) || I18n.default_locale) do
+      Time.use_zone(user.time_zone || ENV['DEFAULT_TIME_ZONE'] || 'UTC', &block)
+    end
   end
 end
diff --git a/app/views/notification_mailer/_status.html.haml b/app/views/notification_mailer/_status.html.haml
index bf38dc9aa2..9def9b22aa 100644
--- a/app/views/notification_mailer/_status.html.haml
+++ b/app/views/notification_mailer/_status.html.haml
@@ -28,4 +28,4 @@
                 = link_to a.remote_url, a.remote_url
 
       %p.email-status-footer
-        = link_to l(status.created_at.in_time_zone(time_zone.presence), format: :with_time_zone), web_url("@#{status.account.pretty_acct}/#{status.id}")
+        = link_to l(status.created_at, format: :with_time_zone), web_url("@#{status.account.pretty_acct}/#{status.id}")
diff --git a/app/views/user_mailer/appeal_approved.html.haml b/app/views/user_mailer/appeal_approved.html.haml
index 54e9a94a54..e4fdd586a3 100644
--- a/app/views/user_mailer/appeal_approved.html.haml
+++ b/app/views/user_mailer/appeal_approved.html.haml
@@ -7,6 +7,6 @@
         %tr
           %td.email-inner-card-td.email-prose
             %p= t 'user_mailer.appeal_approved.explanation',
-                  appeal_date: l(@appeal.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone),
-                  strike_date: l(@appeal.strike.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone)
+                  appeal_date: l(@appeal.created_at, format: :with_time_zone),
+                  strike_date: l(@appeal.strike.created_at, format: :with_time_zone)
             = render 'application/mailer/button', text: t('user_mailer.appeal_approved.action'), url: root_url
diff --git a/app/views/user_mailer/appeal_approved.text.erb b/app/views/user_mailer/appeal_approved.text.erb
index 48fc4b4f75..501e839152 100644
--- a/app/views/user_mailer/appeal_approved.text.erb
+++ b/app/views/user_mailer/appeal_approved.text.erb
@@ -2,6 +2,6 @@
 
 ===
 
-<%= t 'user_mailer.appeal_approved.explanation', appeal_date: l(@appeal.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone), strike_date: l(@appeal.strike.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone) %>
+<%= t 'user_mailer.appeal_approved.explanation', appeal_date: l(@appeal.created_at, format: :with_time_zone), strike_date: l(@appeal.strike.created_at, format: :with_time_zone) %>
 
 => <%= root_url %>
diff --git a/app/views/user_mailer/appeal_rejected.html.haml b/app/views/user_mailer/appeal_rejected.html.haml
index b493712b05..764358a799 100644
--- a/app/views/user_mailer/appeal_rejected.html.haml
+++ b/app/views/user_mailer/appeal_rejected.html.haml
@@ -7,6 +7,6 @@
         %tr
           %td.email-inner-card-td.email-prose
             %p= t 'user_mailer.appeal_rejected.explanation',
-                  appeal_date: l(@appeal.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone),
-                  strike_date: l(@appeal.strike.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone)
+                  appeal_date: l(@appeal.created_at, format: :with_time_zone),
+                  strike_date: l(@appeal.strike.created_at, format: :with_time_zone)
             = render 'application/mailer/button', text: t('user_mailer.appeal_approved.action'), url: root_url
diff --git a/app/views/user_mailer/appeal_rejected.text.erb b/app/views/user_mailer/appeal_rejected.text.erb
index 8b8408e91a..a763a35227 100644
--- a/app/views/user_mailer/appeal_rejected.text.erb
+++ b/app/views/user_mailer/appeal_rejected.text.erb
@@ -2,6 +2,6 @@
 
 ===
 
-<%= t 'user_mailer.appeal_rejected.explanation', appeal_date: l(@appeal.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone), strike_date: l(@appeal.strike.created_at.in_time_zone(@resource.time_zone.presence), format: :with_time_zone) %>
+<%= t 'user_mailer.appeal_rejected.explanation', appeal_date: l(@appeal.created_at, format: :with_time_zone), strike_date: l(@appeal.strike.created_at, format: :with_time_zone) %>
 
 => <%= root_url %>
diff --git a/app/views/user_mailer/failed_2fa.html.haml b/app/views/user_mailer/failed_2fa.html.haml
index e1da35ce06..62b124649e 100644
--- a/app/views/user_mailer/failed_2fa.html.haml
+++ b/app/views/user_mailer/failed_2fa.html.haml
@@ -18,7 +18,7 @@
                     platform: t("sessions.platforms.#{@detection.platform.id}", default: @detection.platform.id.to_s)
               %br/
               %strong #{t('sessions.date')}:
-              = l(@timestamp.in_time_zone(@resource.time_zone.presence), format: :with_time_zone)
+              = l(@timestamp, format: :with_time_zone)
             = render 'application/mailer/button', text: t('settings.account_settings'), url: edit_user_registration_url
       %p= t 'user_mailer.failed_2fa.further_actions_html',
             action: link_to(t('user_mailer.suspicious_sign_in.change_password'), edit_user_registration_url)
diff --git a/app/views/user_mailer/failed_2fa.text.erb b/app/views/user_mailer/failed_2fa.text.erb
index c1dbf7d929..dcf450f08d 100644
--- a/app/views/user_mailer/failed_2fa.text.erb
+++ b/app/views/user_mailer/failed_2fa.text.erb
@@ -8,7 +8,7 @@
 
 <%= t('sessions.ip') %>: <%= @remote_ip %>
 <%= t('sessions.browser') %>: <%= t('sessions.description', browser: t("sessions.browsers.#{@detection.id}", default: "#{@detection.id}"), platform: t("sessions.platforms.#{@detection.platform.id}", default: "#{@detection.platform.id}")) %>
-<%= l(@timestamp.in_time_zone(@resource.time_zone.presence), format: :with_time_zone) %>
+<%= l(@timestamp, format: :with_time_zone) %>
 
 <%= t 'user_mailer.failed_2fa.further_actions_html', action: t('user_mailer.suspicious_sign_in.change_password') %>
 
diff --git a/app/views/user_mailer/suspicious_sign_in.html.haml b/app/views/user_mailer/suspicious_sign_in.html.haml
index deee7a1ce1..c3769b46db 100644
--- a/app/views/user_mailer/suspicious_sign_in.html.haml
+++ b/app/views/user_mailer/suspicious_sign_in.html.haml
@@ -18,7 +18,7 @@
                     platform: t("sessions.platforms.#{@detection.platform.id}", default: @detection.platform.id.to_s)
               %br/
               %strong #{t('sessions.date')}:
-              = l(@timestamp.in_time_zone(@resource.time_zone.presence), format: :with_time_zone)
+              = l(@timestamp, format: :with_time_zone)
             = render 'application/mailer/button', text: t('settings.account_settings'), url: edit_user_registration_url
       %p= t 'user_mailer.suspicious_sign_in.further_actions_html',
             action: link_to(t('user_mailer.suspicious_sign_in.change_password'), edit_user_registration_url)
diff --git a/app/views/user_mailer/suspicious_sign_in.text.erb b/app/views/user_mailer/suspicious_sign_in.text.erb
index 0aa4d227d1..c06936c4e6 100644
--- a/app/views/user_mailer/suspicious_sign_in.text.erb
+++ b/app/views/user_mailer/suspicious_sign_in.text.erb
@@ -8,7 +8,7 @@
 
 <%= t('sessions.ip') %>: <%= @remote_ip %>
 <%= t('sessions.browser') %>: <%= t('sessions.description', browser: t("sessions.browsers.#{@detection.id}", default: "#{@detection.id}"), platform: t("sessions.platforms.#{@detection.platform.id}", default: "#{@detection.platform.id}")) %>
-<%= l(@timestamp.in_time_zone(@resource.time_zone.presence), format: :with_time_zone) %>
+<%= l(@timestamp, format: :with_time_zone) %>
 
 <%= t 'user_mailer.suspicious_sign_in.further_actions_html', action: t('user_mailer.suspicious_sign_in.change_password') %>
 
diff --git a/config/application.rb b/config/application.rb
index 41d33198cc..0013c78858 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -78,13 +78,12 @@ module Mastodon
     # These settings can be overridden in specific environments using the files
     # in config/environments, which are processed later.
     #
+    # config.time_zone = "Central Time (US & Canada)"
     # config.eager_load_paths << Rails.root.join("extras")
 
     # config.paths.add File.join('app', 'api'), glob: File.join('**', '*.rb')
     # config.autoload_paths += Dir[Rails.root.join('app', 'api', '*')]
 
-    config.time_zone = ENV['DEFAULT_TIME_ZONE'] || 'UTC'
-
     config.active_job.queue_adapter = :sidekiq
 
     config.action_mailer.deliver_later_queue_name = 'mailers'
diff --git a/config/initializers/time_zone.rb b/config/initializers/time_zone.rb
new file mode 100644
index 0000000000..5a96c1fd21
--- /dev/null
+++ b/config/initializers/time_zone.rb
@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+
+# Raise if invalid zone is specified
+Time.find_zone!(ENV.fetch('DEFAULT_TIME_ZONE', nil))
diff --git a/spec/mailers/notification_mailer_spec.rb b/spec/mailers/notification_mailer_spec.rb
index eab196166d..6569bc10ce 100644
--- a/spec/mailers/notification_mailer_spec.rb
+++ b/spec/mailers/notification_mailer_spec.rb
@@ -5,8 +5,8 @@ require 'rails_helper'
 RSpec.describe NotificationMailer do
   let(:receiver)       { Fabricate(:user, account_attributes: { username: 'alice' }) }
   let(:sender)         { Fabricate(:account, username: 'bob') }
-  let(:foreign_status) { Fabricate(:status, account: sender, text: 'The body of the foreign status') }
-  let(:own_status)     { Fabricate(:status, account: receiver.account, text: 'The body of the own status') }
+  let(:foreign_status) { Fabricate(:status, account: sender, text: 'The body of the foreign status', created_at: '2024-01-01 12:01Z') }
+  let(:own_status)     { Fabricate(:status, account: receiver.account, text: 'The body of the own status', created_at: '2024-01-01 13:02Z') }
 
   shared_examples 'standard headers' do |type|
     it 'renders the email' do
@@ -38,6 +38,7 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(receiver.account).mention }
 
     include_examples 'localized subject', 'notification_mailer.mention.subject', name: 'bob'
+    include_examples 'timestamp in time zone', '2024-01-01 12:01Z'.to_datetime
     include_examples 'standard headers', 'mention'
     include_examples 'thread headers'
 
@@ -72,6 +73,7 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(own_status.account).favourite }
 
     include_examples 'localized subject', 'notification_mailer.favourite.subject', name: 'bob'
+    include_examples 'timestamp in time zone', '2024-01-01 13:02Z'.to_datetime
     include_examples 'standard headers', 'favourite'
     include_examples 'thread headers'
 
@@ -90,6 +92,7 @@ RSpec.describe NotificationMailer do
     let(:mail) { prepared_mailer_for(own_status.account).reblog }
 
     include_examples 'localized subject', 'notification_mailer.reblog.subject', name: 'bob'
+    include_examples 'timestamp in time zone', '2024-01-01 13:02Z'.to_datetime
     include_examples 'standard headers', 'reblog'
     include_examples 'thread headers'
 
diff --git a/spec/mailers/user_mailer_spec.rb b/spec/mailers/user_mailer_spec.rb
index 0257465817..c2b2cd91cb 100644
--- a/spec/mailers/user_mailer_spec.rb
+++ b/spec/mailers/user_mailer_spec.rb
@@ -3,14 +3,12 @@
 require 'rails_helper'
 
 RSpec.describe UserMailer do
-  let(:receiver) { Fabricate(:user) }
+  let(:receiver) { Fabricate(:user, locale: nil) }
 
   describe '#confirmation_instructions' do
     let(:mail) { described_class.confirmation_instructions(receiver, 'spec') }
 
     it 'renders confirmation instructions' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('devise.mailer.confirmation_instructions.title')))
@@ -45,8 +43,6 @@ RSpec.describe UserMailer do
     let(:mail) { described_class.reset_password_instructions(receiver, 'spec') }
 
     it 'renders reset password instructions' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('devise.mailer.reset_password_instructions.title')))
@@ -61,8 +57,6 @@ RSpec.describe UserMailer do
     let(:mail) { described_class.password_change(receiver) }
 
     it 'renders password change notification' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('devise.mailer.password_change.title')))
@@ -76,8 +70,6 @@ RSpec.describe UserMailer do
     let(:mail) { described_class.email_changed(receiver) }
 
     it 'renders email change notification' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('devise.mailer.email_changed.title')))
@@ -92,8 +84,6 @@ RSpec.describe UserMailer do
     let(:mail)   { described_class.warning(receiver, strike) }
 
     it 'renders warning notification' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('user_mailer.warning.title.suspend', acct: receiver.account.acct)))
@@ -106,8 +96,6 @@ RSpec.describe UserMailer do
     let(:mail) { described_class.webauthn_credential_deleted(receiver, credential) }
 
     it 'renders webauthn credential deleted notification' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('devise.mailer.webauthn_credential.deleted.title')))
@@ -120,12 +108,10 @@ RSpec.describe UserMailer do
   describe '#suspicious_sign_in' do
     let(:ip) { '192.168.0.1' }
     let(:agent) { 'NCSA_Mosaic/2.0 (Windows 3.1)' }
-    let(:timestamp) { Time.now.utc }
+    let(:timestamp) { '2024-01-01 12:34Z'.to_datetime }
     let(:mail) { described_class.suspicious_sign_in(receiver, ip, agent, timestamp) }
 
     it 'renders suspicious sign in notification' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('user_mailer.suspicious_sign_in.explanation')))
@@ -133,17 +119,16 @@ RSpec.describe UserMailer do
 
     include_examples 'localized subject',
                      'user_mailer.suspicious_sign_in.subject'
+    include_examples 'timestamp in time zone', '2024-01-01 12:34Z'.to_datetime
   end
 
   describe '#failed_2fa' do
     let(:ip) { '192.168.0.1' }
     let(:agent) { 'NCSA_Mosaic/2.0 (Windows 3.1)' }
-    let(:timestamp) { Time.now.utc }
+    let(:timestamp) { '2024-01-01 12:34Z'.to_datetime }
     let(:mail) { described_class.failed_2fa(receiver, ip, agent, timestamp) }
 
     it 'renders failed 2FA notification' do
-      receiver.update!(locale: nil)
-
       expect(mail)
         .to be_present
         .and(have_body_text(I18n.t('user_mailer.failed_2fa.explanation')))
@@ -151,10 +136,11 @@ RSpec.describe UserMailer do
 
     include_examples 'localized subject',
                      'user_mailer.failed_2fa.subject'
+    include_examples 'timestamp in time zone', '2024-01-01 12:34Z'.to_datetime
   end
 
   describe '#appeal_approved' do
-    let(:appeal) { Fabricate(:appeal, account: receiver.account, approved_at: Time.now.utc) }
+    let(:appeal) { Fabricate(:appeal, account: receiver.account, created_at: '2024-01-01 12:34Z', approved_at: Time.now.utc) }
     let(:mail) { described_class.appeal_approved(receiver, appeal) }
 
     it 'renders appeal_approved notification' do
@@ -163,10 +149,12 @@ RSpec.describe UserMailer do
         .and(have_subject(I18n.t('user_mailer.appeal_approved.subject', date: I18n.l(appeal.created_at))))
         .and(have_body_text(I18n.t('user_mailer.appeal_approved.title')))
     end
+
+    include_examples 'timestamp in time zone', '2024-01-01 12:34Z'.to_datetime
   end
 
   describe '#appeal_rejected' do
-    let(:appeal) { Fabricate(:appeal, account: receiver.account, rejected_at: Time.now.utc) }
+    let(:appeal) { Fabricate(:appeal, account: receiver.account, created_at: '2024-01-01 12:34Z', rejected_at: Time.now.utc) }
     let(:mail) { described_class.appeal_rejected(receiver, appeal) }
 
     it 'renders appeal_rejected notification' do
@@ -175,6 +163,8 @@ RSpec.describe UserMailer do
         .and(have_subject(I18n.t('user_mailer.appeal_rejected.subject', date: I18n.l(appeal.created_at))))
         .and(have_body_text(I18n.t('user_mailer.appeal_rejected.title')))
     end
+
+    include_examples 'timestamp in time zone', '2024-01-01 12:34Z'.to_datetime
   end
 
   describe '#two_factor_enabled' do
diff --git a/spec/support/examples/mailers.rb b/spec/support/examples/mailers.rb
index a8469f1964..f4e8bc463c 100644
--- a/spec/support/examples/mailers.rb
+++ b/spec/support/examples/mailers.rb
@@ -12,3 +12,30 @@ RSpec.shared_examples 'localized subject' do |*args, **kwrest|
     expect(mail.subject).to eq I18n.t(*args, **kwrest.merge(locale: I18n.default_locale))
   end
 end
+
+RSpec.shared_examples 'timestamp in time zone' do |at|
+  context 'when default time zone is defined' do
+    around do |example|
+      ClimateControl.modify DEFAULT_TIME_ZONE: 'Europe/Athens' do
+        example.run
+      end
+    end
+
+    it 'displays timestamp in time zone of the receiver' do
+      time_zone = 'Europe/Berlin'
+      receiver.update!(time_zone: time_zone)
+      expect(mail)
+        .to have_body_text(at.in_time_zone(time_zone).strftime(I18n.t('time.formats.with_time_zone')))
+    end
+
+    it 'displays timestamp in default time zone if the time zone of the receiver is unavailable' do
+      receiver.update!(time_zone: nil)
+      expect(mail).to have_body_text(at.in_time_zone('Europe/Athens').strftime(I18n.t('time.formats.with_time_zone')))
+    end
+  end
+
+  it 'formats timestamp in UTC' do
+    receiver.update!(time_zone: nil)
+    expect(mail).to have_body_text(at.in_time_zone('UTC').strftime(I18n.t('time.formats.with_time_zone')))
+  end
+end