diff --git a/Gemfile.lock b/Gemfile.lock
index d40cadd..0779004 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -328,6 +328,7 @@ PLATFORMS
   aarch64-linux-musl
   arm64-darwin-22
   arm64-darwin-23
+  arm64-darwin-24
   x86_64-linux
 
 DEPENDENCIES
diff --git a/app/controllers/matches_controller.rb b/app/controllers/matches_controller.rb
index 2acf65f..826043c 100644
--- a/app/controllers/matches_controller.rb
+++ b/app/controllers/matches_controller.rb
@@ -15,6 +15,8 @@ class MatchesController < ApplicationController
               elsif match_params['state'] == 'upcoming'
                 # for every group within the tournament find the match with the lowest position that is of state 'not_started'
                 upcoming_matches = @tournament.stages.find_by(level: -1)&.groups&.map { |g| g.matches.select { |m| m.state == 'not_started' }.min_by(&:position) }
+                # filter out nil values (this may happen if one of the groups already has no upcoming matches)
+                upcoming_matches = upcoming_matches.reject(&:nil?)
                 # if there are none, the group stage is over, so we have to look into the playoff stages
                 if upcoming_matches.nil?
                   next_level = 0
@@ -34,14 +36,12 @@ class MatchesController < ApplicationController
                   m.state == match_params['state']
                 end
               end
-    render json: matches, each_serializer: ExtendedMatchSerializer, include: [
-      'match_scores.team', 'bets', 'stage', 'group'
-    ]
+    render json: matches, each_serializer: ExtendedMatchSerializer, include: %w[match_scores.team bets stage group]
   end
 
   # GET /matches/1
   def show
-    render json: @match, include: ['match_scores.points', 'match_scores.team', 'bets']
+    render json: @match, include: %w[match_scores.points match_scores.team bets]
   end
 
   # PATCH/PUT /matches/1
diff --git a/app/controllers/tournaments_controller.rb b/app/controllers/tournaments_controller.rb
index a40c6bf..2e33843 100644
--- a/app/controllers/tournaments_controller.rb
+++ b/app/controllers/tournaments_controller.rb
@@ -1,11 +1,12 @@
 # frozen_string_literal: true
 
 class TournamentsController < ApplicationController
-  before_action :set_tournament, only: %i[show update destroy]
-  before_action :authenticate_user!, only: %i[create update destroy]
-  before_action -> { require_owner! @tournament.owner }, only: %i[update destroy]
+  before_action :set_tournament, only: %i[show update destroy set_timer_end timer_end]
+  before_action :authenticate_user!, only: %i[create update destroy set_timer_end]
+  before_action -> { require_owner! @tournament.owner }, only: %i[update destroy set_timer_end]
   before_action :validate_create_params, only: %i[create]
   before_action :validate_update_params, only: %i[update]
+  before_action :validate_set_timer_end_params, only: %i[set_timer_end]
   rescue_from ActiveRecord::RecordNotFound, with: :render_not_found_error
 
   # GET /tournaments
@@ -93,8 +94,27 @@ class TournamentsController < ApplicationController
     @tournament.destroy
   end
 
+  # GET /tournaments/:id/timer_end
+  def timer_end
+    render json: { timer_end: @tournament.timer_end }
+  end
+
+  # PATCH /tournaments/:id/set_timer_end
+  def set_timer_end
+    if @tournament.update(timer_end_params)
+      render json: @tournament
+    else
+      render json: @tournament.errors, status: :unprocessable_entity
+    end
+  end
+
+
   private
 
+  def timer_end_params
+    { timer_end: params[:timer_end] }
+  end
+
   def organize_teams_in_groups(teams)
     # each team gets put into a array of teams depending on the group specified in team[:group]
     teams.group_by { |team| team['group'] }.values.map do |group|
@@ -158,3 +178,39 @@ class TournamentsController < ApplicationController
     }, status: :unprocessable_entity
   end
 end
+
+def validate_set_timer_end_params
+  timer_end = params[:timer_end]
+  timer_end_seconds = params[:timer_end_seconds]
+
+  # throw error if both timer_end and timer_end_seconds are present
+  if timer_end.present? && timer_end_seconds.present?
+    return render json: { error: 'Only one of timer_end or timer_end_seconds is allowed' }, status: :unprocessable_entity
+  end
+
+  if timer_end_seconds.present?
+    begin
+      timer_end_seconds = Integer(timer_end_seconds)
+    rescue ArgumentError
+      return render json: { error: 'Invalid seconds format' }, status: :unprocessable_entity
+    end
+
+    return render json: { error: 'Timer end must be in the future' }, status: :unprocessable_entity if timer_end_seconds <= 0
+
+    parsed_time = Time.zone.now + timer_end_seconds
+    params[:timer_end] = parsed_time
+  elsif timer_end.present?
+    begin
+      parsed_time = Time.zone.parse(timer_end)
+      if parsed_time.nil?
+        return render json: { error: 'Invalid datetime format' }, status: :unprocessable_entity
+      elsif !parsed_time.future?
+        return render json: { error: 'Timer end must be in the future' }, status: :unprocessable_entity
+      end
+    rescue ArgumentError
+      return render json: { error: 'Invalid datetime format' }, status: :unprocessable_entity
+    end
+  else
+    return render json: { error: 'Timer end is required' }, status: :unprocessable_entity
+  end
+end
diff --git a/app/serializers/tournament_serializer.rb b/app/serializers/tournament_serializer.rb
index df02e38..751aa4f 100644
--- a/app/serializers/tournament_serializer.rb
+++ b/app/serializers/tournament_serializer.rb
@@ -2,7 +2,7 @@
 
 class TournamentSerializer < SimpleTournamentSerializer
   attributes :description, :playoff_teams_amount,
-             :instant_finalists_amount, :intermediate_round_participants_amount
+             :instant_finalists_amount, :intermediate_round_participants_amount, :timer_end
   has_many :stages
 
   attribute :owner_username do
diff --git a/config/routes.rb b/config/routes.rb
index 101e869..9a6cf02 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -14,6 +14,10 @@ Rails.application.routes.draw do
   resources :tournaments do
     resources :statistics, only: %i[index]
     resources :matches, only: %i[index]
+    member do
+      get :timer_end
+      patch :set_timer_end
+    end
   end
   resources :match_scores, only: %i[show update]
   resources :groups, only: %i[show]
diff --git a/db/migrate/20250309202658_add_timer_end_to_tournaments.rb b/db/migrate/20250309202658_add_timer_end_to_tournaments.rb
new file mode 100644
index 0000000..1762bec
--- /dev/null
+++ b/db/migrate/20250309202658_add_timer_end_to_tournaments.rb
@@ -0,0 +1,5 @@
+class AddTimerEndToTournaments < ActiveRecord::Migration[7.0]
+  def change
+    add_column :tournaments, :timer_end, :datetime
+  end
+end
diff --git a/spec/controllers/matches_controller_spec.rb b/spec/controllers/matches_controller_spec.rb
index ec9c725..1beabe4 100644
--- a/spec/controllers/matches_controller_spec.rb
+++ b/spec/controllers/matches_controller_spec.rb
@@ -43,6 +43,7 @@ RSpec.describe MatchesController, type: :controller do
         expect(body.empty?).to be true
       end
     end
+    # TODO add test for upcoming once there is test data for a "valid" group stage
   end
 
   describe 'GET #show' do
diff --git a/spec/controllers/tournaments_controller_spec.rb b/spec/controllers/tournaments_controller_spec.rb
index 1663157..918c39d 100644
--- a/spec/controllers/tournaments_controller_spec.rb
+++ b/spec/controllers/tournaments_controller_spec.rb
@@ -102,6 +102,9 @@ RSpec.describe TournamentsController, type: :controller do
       get :show, params: { id: @tournament.to_param }
       json = deserialize_response(response)
       expect(json[:id].to_i).to eq(@tournament.id)
+      expected_keys = %i[id name code public description playoff_teams_amount instant_finalists_amount intermediate_round_participants_amount timer_end owner_username stages teams]
+      expect(json.keys).to match_array(expected_keys)
+      expect(json).to eq(TournamentSerializer.new(@tournament).as_json)
       expect(json[:name]).to eq(@tournament.name)
       expect(json[:description]).to eq(@tournament.description)
       expect(json[:public]).to eq(@tournament.public)
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index 18608f5..15c095d 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -39,6 +39,7 @@ RSpec.configure do |config|
   config.fixture_path = "#{::Rails.root}/spec/fixtures"
 
   # Run only focused tests
+  # TODO REVERT ME
   config.filter_run_when_matching :focus
 
   # If you're not using ActiveRecord, or you'd prefer not to run each of your