diff --git a/app/controllers/tournaments_controller.rb b/app/controllers/tournaments_controller.rb
index aaabd93..f12b169 100644
--- a/app/controllers/tournaments_controller.rb
+++ b/app/controllers/tournaments_controller.rb
@@ -173,14 +173,14 @@ class TournamentsController < ApplicationController
 
   def timer_end_params
     {
-      timer_end: params[:timer_end],
+      timer_end: params[:timer_end] || params[:timestamp],
       timer_mode: params[:timer_mode]
     }
   end
 
   def serialize_timer_state(tournament)
     {
-      timer_end: tournament.timer_end&.iso8601,
+      timestamp: tournament.timer_end&.iso8601,
       timer_mode: tournament.timer_mode
     }
   end
@@ -333,14 +333,17 @@ class TournamentsController < ApplicationController
   end
 
   def validate_set_timer_end_params
-    timer_end = params[:timer_end]
-    timer_end_seconds = params[:timer_end_seconds]
+    timestamp = params[:timestamp]
+    timestamp_seconds = params[:timestamp_seconds]
     timer_mode = params[:timer_mode]
     clear_timer = ActiveModel::Type::Boolean.new.cast(params[:clear_timer])
 
+    timestamp = params[:timer_end] if timestamp.blank? && params[:timer_end].present?
+    timestamp_seconds = params[:timer_end_seconds] if timestamp_seconds.blank? && params[:timer_end_seconds].present?
+
     if clear_timer
-      if timer_end.present? || timer_end_seconds.present? || timer_mode.present?
-        return render json: { error: 'clear_timer cannot be combined with timer values or timer_mode' },
+      if timestamp.present? || timestamp_seconds.present? || timer_mode.present?
+        return render json: { error: 'clear_timer cannot be combined with timestamp values or timer_mode' },
                       status: :unprocessable_entity
       end
 
@@ -353,48 +356,48 @@ class TournamentsController < ApplicationController
       return render json: { error: 'Invalid timer_mode' }, status: :unprocessable_entity
     end
 
-    # 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
+    # throw error if both timestamp and timestamp_seconds are present
+    if timestamp.present? && timestamp_seconds.present?
+      return render json: { error: 'Only one of timestamp or timestamp_seconds is allowed' }, status: :unprocessable_entity
     end
 
-    if timer_mode == 'countup' && timer_end_seconds.present?
-      return render json: { error: 'timer_end_seconds is only allowed for countdown mode' }, status: :unprocessable_entity
+    if timer_mode == 'countup' && timestamp_seconds.present?
+      return render json: { error: 'timestamp_seconds is only allowed for countdown mode' }, status: :unprocessable_entity
     end
 
-    if timer_end_seconds.present?
+    if timestamp_seconds.present?
       begin
-        timer_end_seconds = Integer(timer_end_seconds)
+        timestamp_seconds = Integer(timestamp_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
+      return render json: { error: 'Timestamp must be in the future for countdown mode' }, status: :unprocessable_entity if timestamp_seconds <= 0
 
-      parsed_time = Time.zone.now + timer_end_seconds
+      parsed_time = Time.zone.now + timestamp_seconds
       params[:timer_end] = parsed_time
       params[:timer_mode] = 'countdown'
-    elsif timer_end.present?
+    elsif timestamp.present?
       begin
-        parsed_time = Time.zone.parse(timer_end)
+        parsed_time = Time.zone.parse(timestamp)
         if parsed_time.nil?
-          return render json: { error: 'Invalid timer_end format' }, status: :unprocessable_entity
+          return render json: { error: 'Invalid timestamp format' }, status: :unprocessable_entity
         elsif timer_mode != 'countup' && !parsed_time.future?
-          return render json: { error: 'Timer end must be in the future' }, status: :unprocessable_entity
+          return render json: { error: 'Timestamp must be in the future for countdown mode' }, status: :unprocessable_entity
         end
 
         params[:timer_end] = parsed_time
         params[:timer_mode] = timer_mode.presence || 'countdown'
       rescue ArgumentError
-        return render json: { error: 'Invalid timer_end format' }, status: :unprocessable_entity
+        return render json: { error: 'Invalid timestamp format' }, status: :unprocessable_entity
       end
     elsif timer_mode == 'countup'
       params[:timer_end] = Time.zone.now
     elsif timer_mode.present?
-      return render json: { error: 'timer_mode requires timer_end, timer_end_seconds, or clear_timer' },
+      return render json: { error: 'timer_mode requires timestamp, timestamp_seconds, or clear_timer' },
                     status: :unprocessable_entity
     else
-      return render json: { error: 'timer_end, timer_end_seconds, or clear_timer is required' },
+      return render json: { error: 'timestamp, timestamp_seconds, or clear_timer is required' },
                     status: :unprocessable_entity
     end
   end
diff --git a/app/serializers/tournament_serializer.rb b/app/serializers/tournament_serializer.rb
index abed8eb..e5d525a 100644
--- a/app/serializers/tournament_serializer.rb
+++ b/app/serializers/tournament_serializer.rb
@@ -11,7 +11,7 @@ class TournamentSerializer < SimpleTournamentSerializer
   has_many :stages
   has_many :team_action_lists
 
-  attribute :timer_end do
+  attribute :timestamp do
     object.timer_end&.iso8601
   end
 
diff --git a/app/services/tournament_snapshot_builder.rb b/app/services/tournament_snapshot_builder.rb
index 03a5226..9932cc8 100644
--- a/app/services/tournament_snapshot_builder.rb
+++ b/app/services/tournament_snapshot_builder.rb
@@ -22,7 +22,7 @@ class TournamentSnapshotBuilder
 
   def build
     payload = tournament.attributes.symbolize_keys.slice(*ROOT_ATTRIBUTES)
-    payload[:timer_end] = tournament.timer_end&.iso8601
+    payload[:timestamp] = tournament.timer_end&.iso8601
     payload[:timer_mode] = tournament.timer_mode
     payload[:sync_generated_at] = Time.current.iso8601(6)
     payload[:teams] = teams_payload
diff --git a/app/services/tournament_snapshot_importer.rb b/app/services/tournament_snapshot_importer.rb
index 4841792..4e1af83 100644
--- a/app/services/tournament_snapshot_importer.rb
+++ b/app/services/tournament_snapshot_importer.rb
@@ -67,7 +67,7 @@ class TournamentSnapshotImporter
   def update_tournament!
     root_attrs = snapshot.slice(*ROOT_ATTRIBUTES)
     root_attrs[:code] = tournament.code if code_taken_by_another_tournament?(root_attrs[:code])
-    root_attrs[:timer_end] = parse_time(snapshot[:timer_end])
+    root_attrs[:timer_end] = parse_time(snapshot[:timestamp] || snapshot[:timer_end])
     root_attrs[:timer_mode] = snapshot[:timer_mode]
     root_attrs[:sync_source_tournament_id] = snapshot[:id]
     root_attrs[:sync_last_imported_snapshot_at] = snapshot_generated_at
diff --git a/app/services/tournament_timer_broadcast_payload.rb b/app/services/tournament_timer_broadcast_payload.rb
index 5640165..97fa866 100644
--- a/app/services/tournament_timer_broadcast_payload.rb
+++ b/app/services/tournament_timer_broadcast_payload.rb
@@ -6,7 +6,7 @@ class TournamentTimerBroadcastPayload
       {
         type: 'timer.updated',
         tournament_id: tournament.id,
-        timer_end: tournament.timer_end&.iso8601,
+        timestamp: tournament.timer_end&.iso8601,
         timer_mode: tournament.timer_mode
       }
     end
diff --git a/doc/timer_api.md b/doc/timer_api.md
index 8e63d04..3f170fd 100644
--- a/doc/timer_api.md
+++ b/doc/timer_api.md
@@ -10,9 +10,9 @@ Backend timer supports:
 - live websocket updates
 - follower sync propagation
 
-Frontend should treat timer state as small state machine:
+Frontend should treat timer state as:
 
-- no timer: `timer_end = null`, `timer_mode = null`
+- no timer: `timestamp = null`, `timer_mode = null`
 - countdown: `timer_mode = "countdown"`
 - countup: `timer_mode = "countup"`
 
@@ -30,7 +30,7 @@ Response shape:
 
 ```json
 {
-  "timer_end": "2026-04-24T10:15:00Z",
+  "timestamp": "2026-04-24T10:15:00Z",
   "timer_mode": "countdown"
 }
 ```
@@ -41,23 +41,23 @@ Possible values:
 - `timer_mode = "countup"`
 - `timer_mode = null`
 
-## Meaning Of `timer_end`
+## Meaning Of `timestamp`
 
-Name old. Semantics now depend on mode.
+Same field. Mode decides meaning.
 
 ### Countdown mode
 
-`timer_end` means exact wall-clock timestamp when countdown reaches zero.
+`timestamp` means exact wall-clock timestamp when countdown reaches zero.
 
 Frontend math:
 
 ```text
-remaining_ms = max(0, timer_end - now)
+remaining_ms = max(0, timestamp - now)
 ```
 
 ### Countup mode
 
-`timer_end` means anchor timestamp when countup started.
+`timestamp` means anchor timestamp when countup started.
 
 It is **not** finish time in this mode.
 Think of it as:
@@ -68,23 +68,23 @@ Think of it as:
 Frontend math:
 
 ```text
-elapsed_ms = max(0, now - timer_end)
+elapsed_ms = max(0, now - timestamp)
 ```
 
 Practical example:
 
 - backend returns:
   - `timer_mode = "countup"`
-  - `timer_end = "2026-04-24T10:00:00Z"`
+  - `timestamp = "2026-04-24T10:00:00Z"`
 - current time:
-  - `2026-04-24T10:03:15Z"`
+  - `2026-04-24T10:03:15Z`
 
 Frontend should display about `03:15` elapsed.
 
 ### Unset timer
 
 - `timer_mode = null`
-- `timer_end = null`
+- `timestamp = null`
 
 Frontend should render no active timer.
 
@@ -97,13 +97,16 @@ Endpoint:
 
 - `PATCH /tournaments/:id/set_timer_end`
 
+Current route name still says `set_timer_end`.
+Payload field name is now `timestamp`.
+
 ### Start countdown by duration
 
 Request:
 
 ```json
 {
-  "timer_end_seconds": 120
+  "timestamp_seconds": 120
 }
 ```
 
@@ -112,7 +115,7 @@ Behavior:
 - backend computes `Time.zone.now + 120`
 - backend stores:
   - `timer_mode = "countdown"`
-  - `timer_end = computed future timestamp`
+  - `timestamp = computed future timestamp`
 
 ### Start countdown by explicit timestamp
 
@@ -120,7 +123,7 @@ Request:
 
 ```json
 {
-  "timer_end": "2026-04-24T10:15:00Z"
+  "timestamp": "2026-04-24T10:15:00Z"
 }
 ```
 
@@ -128,7 +131,7 @@ Optional explicit mode:
 
 ```json
 {
-  "timer_end": "2026-04-24T10:15:00Z",
+  "timestamp": "2026-04-24T10:15:00Z",
   "timer_mode": "countdown"
 }
 ```
@@ -145,10 +148,10 @@ Request:
 
 Behavior:
 
-- backend stores current server time into `timer_end`
+- backend stores current server time into `timestamp`
 - backend stores `timer_mode = "countup"`
 
-Frontend should interpret returned `timer_end` as start time anchor.
+Frontend should interpret returned `timestamp` as start time anchor.
 
 ### Restore countup from explicit anchor
 
@@ -156,7 +159,7 @@ Backend also accepts explicit timestamp with countup mode:
 
 ```json
 {
-  "timer_end": "2026-04-24T10:00:00Z",
+  "timestamp": "2026-04-24T10:00:00Z",
   "timer_mode": "countup"
 }
 ```
@@ -181,17 +184,17 @@ Behavior:
 
 - backend clears both fields
 - response returns:
-  - `timer_end = null`
+  - `timestamp = null`
   - `timer_mode = null`
 
 ## Validation Rules
 
 Backend rejects:
 
-- both `timer_end` and `timer_end_seconds`
+- both `timestamp` and `timestamp_seconds`
 - invalid `timer_mode`
-- `timer_end_seconds <= 0`
-- `timer_end_seconds` together with `timer_mode = "countup"`
+- `timestamp_seconds <= 0`
+- `timestamp_seconds` together with `timer_mode = "countup"`
 - `timer_mode` by itself unless it is `countup`
 - `clear_timer` mixed with timer values
 
@@ -222,7 +225,7 @@ Payload:
 {
   "type": "timer.updated",
   "tournament_id": 123,
-  "timer_end": "2026-04-24T10:15:00Z",
+  "timestamp": "2026-04-24T10:15:00Z",
   "timer_mode": "countdown"
 }
 ```
@@ -243,35 +246,35 @@ Frontend rule:
 Recommended flow:
 
 1. Load tournament via `GET /tournaments/:id`
-2. Read `timer_mode` and `timer_end`
+2. Read `timer_mode` and `timestamp`
 3. Open ActionCable subscription for same tournament id
 4. Replace local timer state whenever `timer.updated` arrives
-5. Derive displayed time from `Date.now()` plus stored server timestamp
+5. Derive displayed time from `Date.now()` plus stored backend timestamp
 
 Recommended client state:
 
 ```ts
 type TimerState =
-  | { mode: null; anchorIso: null }
-  | { mode: "countdown"; anchorIso: string }
-  | { mode: "countup"; anchorIso: string };
+  | { mode: null; timestampIso: null }
+  | { mode: "countdown"; timestampIso: string }
+  | { mode: "countup"; timestampIso: string };
 ```
 
 Suggested derivation logic:
 
 ```ts
 function getTimerDisplay(state: TimerState, nowMs: number) {
-  if (state.mode === null || state.anchorIso === null) {
+  if (state.mode === null || state.timestampIso === null) {
     return { active: false, ms: 0 };
   }
 
-  const anchorMs = new Date(state.anchorIso).getTime();
+  const timestampMs = new Date(state.timestampIso).getTime();
 
   if (state.mode === "countdown") {
-    return { active: true, ms: Math.max(0, anchorMs - nowMs) };
+    return { active: true, ms: Math.max(0, timestampMs - nowMs) };
   }
 
-  return { active: true, ms: Math.max(0, nowMs - anchorMs) };
+  return { active: true, ms: Math.max(0, nowMs - timestampMs) };
 }
 ```
 
@@ -284,13 +287,13 @@ Recommended rendering:
 Recommended local ticking:
 
 - keep backend state as timestamp + mode
-- update rendered value with 250ms or 1s local interval
+- update rendered value with local interval
 - do not poll backend every second
 
 Recommended write UX:
 
 - owner actions send explicit target request
-- after successful response, update local state from response body
+- after success, update local state from response body
 - websocket should converge all viewers to same state
 
 ## Follower Behavior
@@ -300,7 +303,7 @@ Timer state is included in tournament sync snapshots.
 That means:
 
 - leader timer changes propagate to follower
-- follower tournament exposes same `timer_end` / `timer_mode`
+- follower tournament exposes same `timestamp` / `timer_mode`
 - follower websocket subscribers receive `timer.updated`
 - follower still rejects timer writes while read only
 
@@ -322,4 +325,4 @@ Implemented coverage:
 Current note:
 
 - single-backend HTTP E2E timer specs pass
-- follower blackbox task still has environment/network issue in existing Docker follow setup, so production-style follow stack verification is not green yet
+- follower blackbox task still has existing Docker/network issue in follow setup, so production-style follow stack verification is not green yet
diff --git a/e2e/lib/scenario_runner.rb b/e2e/lib/scenario_runner.rb
index d6d3b24..9ad0682 100644
--- a/e2e/lib/scenario_runner.rb
+++ b/e2e/lib/scenario_runner.rb
@@ -30,9 +30,9 @@ module TurniereE2E
 
       timer_response = patch!(
         "/tournaments/#{tournament.fetch(:id)}/set_timer_end",
-        body: { timer_end_seconds: 600 }
+        body: { timestamp_seconds: 600 }
       )
-      checkpoints[:timer_set] = { timer_end: timer_response.fetch(:timer_end) }
+      checkpoints[:timer_set] = { timestamp: timer_response.fetch(:timestamp) }
       return result(session: session, tournament: tournament, checkpoints: checkpoints, stop_at: stop_at) if stop_at == :timer_set
 
       upcoming_matches = get!(
diff --git a/spec/controllers/tournaments_controller_spec.rb b/spec/controllers/tournaments_controller_spec.rb
index 99fb5b7..f4c31cf 100644
--- a/spec/controllers/tournaments_controller_spec.rb
+++ b/spec/controllers/tournaments_controller_spec.rb
@@ -105,7 +105,7 @@ RSpec.describe TournamentsController, type: :controller do
       expected_keys = %i[
         id name code public description playoff_teams_amount
         instant_finalists_amount intermediate_round_participants_amount
-        timer_end timer_mode owner_username stages teams team_action_lists
+        timestamp timer_mode owner_username stages teams team_action_lists
       ]
       expect(json.keys).to match_array(expected_keys)
       expect(json[:name]).to eq(@tournament.name)
@@ -228,7 +228,7 @@ RSpec.describe TournamentsController, type: :controller do
       get :timer_end, params: { id: @tournament.to_param }
 
       expect(response).to be_successful
-      expect(deserialize_response(response)[:timer_end]).to eq(timer_end.iso8601)
+      expect(deserialize_response(response)[:timestamp]).to eq(timer_end.iso8601)
       expect(deserialize_response(response)[:timer_mode]).to eq('countdown')
     end
   end
@@ -238,14 +238,14 @@ RSpec.describe TournamentsController, type: :controller do
       apply_authentication_headers_for @user
     end
 
-    it 'stores timezone-aware timer_end values without shifting them' do
-      timer_end = '2030-04-13T18:00:00+02:00'
+    it 'stores timezone-aware timestamp values without shifting them' do
+      timestamp = '2030-04-13T18:00:00+02:00'
 
-      patch :set_timer_end, params: { id: @tournament.to_param, timer_end: timer_end }
+      patch :set_timer_end, params: { id: @tournament.to_param, timestamp: timestamp }
 
       expect(response).to be_successful
-      expect(@tournament.reload.timer_end.iso8601).to eq(Time.iso8601(timer_end).utc.iso8601)
-      expect(deserialize_response(response)[:timer_end]).to eq(@tournament.timer_end.iso8601)
+      expect(@tournament.reload.timer_end.iso8601).to eq(Time.iso8601(timestamp).utc.iso8601)
+      expect(deserialize_response(response)[:timestamp]).to eq(@tournament.timer_end.iso8601)
       expect(deserialize_response(response)[:timer_mode]).to eq('countdown')
     end
 
@@ -268,15 +268,15 @@ RSpec.describe TournamentsController, type: :controller do
       expect(response).to be_successful
       expect(@tournament.reload.timer_end).to be_nil
       expect(@tournament.timer_mode).to be_nil
-      expect(deserialize_response(response)[:timer_end]).to be_nil
+      expect(deserialize_response(response)[:timestamp]).to be_nil
       expect(deserialize_response(response)[:timer_mode]).to be_nil
     end
 
-    it 'rejects timer_end_seconds for countup mode' do
-      patch :set_timer_end, params: { id: @tournament.to_param, timer_mode: 'countup', timer_end_seconds: 120 }
+    it 'rejects timestamp_seconds for countup mode' do
+      patch :set_timer_end, params: { id: @tournament.to_param, timer_mode: 'countup', timestamp_seconds: 120 }
 
       expect(response).to have_http_status(:unprocessable_entity)
-      expect(deserialize_response(response)[:error]).to eq('timer_end_seconds is only allowed for countdown mode')
+      expect(deserialize_response(response)[:error]).to eq('timestamp_seconds is only allowed for countdown mode')
     end
   end
 
diff --git a/spec/e2e/http/api_surface_spec.rb b/spec/e2e/http/api_surface_spec.rb
index e6be9a3..7db4ad6 100644
--- a/spec/e2e/http/api_surface_spec.rb
+++ b/spec/e2e/http/api_surface_spec.rb
@@ -125,21 +125,21 @@ RSpec.describe 'Backend API surface HTTP E2E' do
     forbidden_update = other_client.patch("/tournaments/#{tournament.fetch(:id)}", body: { name: 'Not Allowed' })
     unauthenticated_update = anonymous_client.patch("/tournaments/#{tournament.fetch(:id)}", body: { name: 'No Auth' })
 
-    timer_seconds = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_end_seconds: 120 })
+    timer_seconds = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timestamp_seconds: 120 })
     timer_show = anonymous_client.get("/tournaments/#{tournament.fetch(:id)}/timer_end")
     timer_countup = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_mode: 'countup' })
     timer_clear = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { clear_timer: true })
     timer_double = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: {
-                                        timer_end_seconds: 120,
-                                        timer_end: (Time.now.utc + 240).iso8601
+                                        timestamp_seconds: 120,
+                                        timestamp: (Time.now.utc + 240).iso8601
                                       })
-    timer_invalid_seconds = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_end_seconds: 'nope' })
-    timer_past = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_end_seconds: 0 })
+    timer_invalid_seconds = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timestamp_seconds: 'nope' })
+    timer_past = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timestamp_seconds: 0 })
     timer_countup_seconds = owner_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: {
                                                  timer_mode: 'countup',
-                                                 timer_end_seconds: 60
+                                                 timestamp_seconds: 60
                                                })
-    timer_forbidden = other_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_end_seconds: 60 })
+    timer_forbidden = other_client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timestamp_seconds: 60 })
 
     destroy_response = owner_client.delete("/tournaments/#{tournament.fetch(:id)}")
     after_destroy = anonymous_client.get("/tournaments/#{tournament.fetch(:id)}")
@@ -160,26 +160,26 @@ RSpec.describe 'Backend API surface HTTP E2E' do
     expect(unauthenticated_update[:status]).to eq(401)
 
     expect(timer_seconds[:status]).to eq(200)
-    expect(timer_seconds.dig(:json, :timer_end)).to be_a(String)
+    expect(timer_seconds.dig(:json, :timestamp)).to be_a(String)
     expect(timer_seconds.dig(:json, :timer_mode)).to eq('countdown')
     expect(timer_show[:status]).to eq(200)
-    expect(timer_show.dig(:json, :timer_end)).to eq(timer_seconds.dig(:json, :timer_end))
+    expect(timer_show.dig(:json, :timestamp)).to eq(timer_seconds.dig(:json, :timestamp))
     expect(timer_show.dig(:json, :timer_mode)).to eq('countdown')
     expect(timer_countup[:status]).to eq(200)
-    expect(timer_countup.dig(:json, :timer_end)).to be_a(String)
+    expect(timer_countup.dig(:json, :timestamp)).to be_a(String)
     expect(timer_countup.dig(:json, :timer_mode)).to eq('countup')
     expect(timer_clear[:status]).to eq(200)
-    expect(timer_clear.dig(:json, :timer_end)).to be_nil
+    expect(timer_clear.dig(:json, :timestamp)).to be_nil
     expect(timer_clear.dig(:json, :timer_mode)).to be_nil
 
     expect(timer_double[:status]).to eq(422)
-    expect(timer_double.dig(:json, :error)).to eq('Only one of timer_end or timer_end_seconds is allowed')
+    expect(timer_double.dig(:json, :error)).to eq('Only one of timestamp or timestamp_seconds is allowed')
     expect(timer_invalid_seconds[:status]).to eq(422)
     expect(timer_invalid_seconds.dig(:json, :error)).to eq('Invalid seconds format')
     expect(timer_past[:status]).to eq(422)
-    expect(timer_past.dig(:json, :error)).to eq('Timer end must be in the future')
+    expect(timer_past.dig(:json, :error)).to eq('Timestamp must be in the future for countdown mode')
     expect(timer_countup_seconds[:status]).to eq(422)
-    expect(timer_countup_seconds.dig(:json, :error)).to eq('timer_end_seconds is only allowed for countdown mode')
+    expect(timer_countup_seconds.dig(:json, :error)).to eq('timestamp_seconds is only allowed for countdown mode')
     expect(timer_forbidden[:status]).to eq(403)
 
     expect([200, 204]).to include(destroy_response[:status])
diff --git a/spec/e2e/http/tournament_follow_sync_spec.rb b/spec/e2e/http/tournament_follow_sync_spec.rb
index 1802516..90edc01 100644
--- a/spec/e2e/http/tournament_follow_sync_spec.rb
+++ b/spec/e2e/http/tournament_follow_sync_spec.rb
@@ -474,7 +474,7 @@ RSpec.describe 'Tournament follower sync HTTP E2E' do
       playoff_teams_amount: tournament.fetch(:playoff_teams_amount),
       instant_finalists_amount: tournament.fetch(:instant_finalists_amount),
       intermediate_round_participants_amount: tournament.fetch(:intermediate_round_participants_amount),
-      timer_end: tournament[:timer_end],
+      timestamp: tournament[:timestamp],
       teams: tournament.fetch(:teams).map { |team| team.slice(:name, :advancing_from_group_stage) }.sort_by { |team| team.fetch(:name) },
       team_action_lists: tournament.fetch(:team_action_lists, []).sort_by { |list| list.fetch(:key) }.map do |list|
         {
diff --git a/spec/e2e/http/tournament_timer_follow_sync_websocket_spec.rb b/spec/e2e/http/tournament_timer_follow_sync_websocket_spec.rb
index 2511b83..c8e43db 100644
--- a/spec/e2e/http/tournament_timer_follow_sync_websocket_spec.rb
+++ b/spec/e2e/http/tournament_timer_follow_sync_websocket_spec.rb
@@ -38,26 +38,26 @@ RSpec.describe 'Tournament timer follower sync websocket HTTP E2E' do
     cable_client = TurniereE2E::ActionCableClient.new(base_url: follower_base_url)
     cable_client.subscribe_timer!(tournament_id: follower.fetch(:id))
     initial_payload = cable_client.wait_for_timer_payload!
-    expect(initial_payload.fetch('timer_end')).to be_nil
+    expect(initial_payload.fetch('timestamp')).to be_nil
     expect(initial_payload.fetch('timer_mode')).to be_nil
 
-    countdown = source_client.patch("/tournaments/#{source.fetch(:id)}/set_timer_end", body: { timer_end_seconds: 120 })
+    countdown = source_client.patch("/tournaments/#{source.fetch(:id)}/set_timer_end", body: { timestamp_seconds: 120 })
     expect(countdown[:status]).to eq(200)
 
     countdown_payload = wait_for_timer_state!(cable_client, timer_mode: 'countdown')
-    expect(countdown_payload.fetch('timer_end')).to eq(countdown.dig(:json, :timer_end))
+    expect(countdown_payload.fetch('timestamp')).to eq(countdown.dig(:json, :timestamp))
 
     countup = source_client.patch("/tournaments/#{source.fetch(:id)}/set_timer_end", body: { timer_mode: 'countup' })
     expect(countup[:status]).to eq(200)
 
     countup_payload = wait_for_timer_state!(cable_client, timer_mode: 'countup')
-    expect(countup_payload.fetch('timer_end')).to eq(countup.dig(:json, :timer_end))
+    expect(countup_payload.fetch('timestamp')).to eq(countup.dig(:json, :timestamp))
 
     clear = source_client.patch("/tournaments/#{source.fetch(:id)}/set_timer_end", body: { clear_timer: true })
     expect(clear[:status]).to eq(200)
 
     cleared_payload = wait_for_timer_state!(cable_client, timer_mode: nil)
-    expect(cleared_payload.fetch('timer_end')).to be_nil
+    expect(cleared_payload.fetch('timestamp')).to be_nil
   ensure
     cable_client&.close
   end
diff --git a/spec/e2e/http/tournament_timer_websocket_spec.rb b/spec/e2e/http/tournament_timer_websocket_spec.rb
index 9fd18c3..f9d423e 100644
--- a/spec/e2e/http/tournament_timer_websocket_spec.rb
+++ b/spec/e2e/http/tournament_timer_websocket_spec.rb
@@ -29,26 +29,26 @@ RSpec.describe 'Tournament timer websocket HTTP E2E' do
     cable_client.subscribe_timer!(tournament_id: tournament.fetch(:id))
 
     initial_payload = cable_client.wait_for_timer_payload!
-    expect(initial_payload.fetch('timer_end')).to be_nil
+    expect(initial_payload.fetch('timestamp')).to be_nil
     expect(initial_payload.fetch('timer_mode')).to be_nil
 
-    countdown = client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_end_seconds: 120 })
+    countdown = client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timestamp_seconds: 120 })
     expect(countdown[:status]).to eq(200)
 
     countdown_payload = wait_for_timer_state!(cable_client, timer_mode: 'countdown')
-    expect(countdown_payload.fetch('timer_end')).to eq(countdown.dig(:json, :timer_end))
+    expect(countdown_payload.fetch('timestamp')).to eq(countdown.dig(:json, :timestamp))
 
     countup = client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { timer_mode: 'countup' })
     expect(countup[:status]).to eq(200)
 
     countup_payload = wait_for_timer_state!(cable_client, timer_mode: 'countup')
-    expect(countup_payload.fetch('timer_end')).to eq(countup.dig(:json, :timer_end))
+    expect(countup_payload.fetch('timestamp')).to eq(countup.dig(:json, :timestamp))
 
     clear = client.patch("/tournaments/#{tournament.fetch(:id)}/set_timer_end", body: { clear_timer: true })
     expect(clear[:status]).to eq(200)
 
     cleared_payload = wait_for_timer_state!(cable_client, timer_mode: nil)
-    expect(cleared_payload.fetch('timer_end')).to be_nil
+    expect(cleared_payload.fetch('timestamp')).to be_nil
   ensure
     cable_client&.close
   end
diff --git a/spec/services/tournament_snapshot_importer_spec.rb b/spec/services/tournament_snapshot_importer_spec.rb
index 25d9d0b..4c9d1ef 100644
--- a/spec/services/tournament_snapshot_importer_spec.rb
+++ b/spec/services/tournament_snapshot_importer_spec.rb
@@ -183,7 +183,7 @@ RSpec.describe TournamentSnapshotImporter do
       playoff_teams_amount: tournament.playoff_teams_amount,
       instant_finalists_amount: tournament.instant_finalists_amount,
       intermediate_round_participants_amount: tournament.intermediate_round_participants_amount,
-      timer_end: tournament.timer_end&.iso8601,
+      timestamp: tournament.timer_end&.iso8601,
       timer_mode: tournament.timer_mode,
       teams: tournament.teams.order(:name).map { |team| team.name },
       team_action_lists: tournament.team_action_lists.order(:key).map do |list|