diff --git a/CHANGELOG.md b/CHANGELOG.md
index df85442e5..075c45b46 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,9 @@ Format based on [Keep a Changelog](https://keepachangelog.com/).
 - Insert/HUD wireframe and visual spec (#314) — dual character variants (smuggler social network view, detective investigation overlay) with pixel-precise layout, entity markers, time display, border arrows, commission grid, and all interaction states
 - Contradiction monologue lines — 16 hand-authored lines (8 detective, 8 smuggler) for Sera/Kael FRIEND arc, Phase 2 blindsiding + Phase 3 pattern recognition, cognitive-dissonance-not-accusation tone per D-083 (#552)
 - Diegetic tutorial monologue — 20 lines (10 per character) teaching movement, fog, sound, NPC interaction, and insert/HUD through character voice, fire-once on first-time events (#330)
+- Diegetic time display on insert HUD — station local time (HH:MM), day phase with cycle-tinted color, day number on InsertOverlay (#263)
+- Relationship color accent on E-Talk overlay — 3px left-edge bar using D-033 palette signals NPC relationship at a glance (#537)
+- `Constants.format_game_time()` helper for converting game-minutes to HH:MM station time
 - `/sprint-status` cleanup sweep skill — consistent health report with tickets by status, PR cross-reference, bookkeeping issue detection, and open work by team
 - `sprint sweep` CLI subcommand — structured JSON output for sprint health checks (grouped tickets, per-team summary, issue detection)
 - Knowledge Flow & NPC Boundaries workshop — 5 D-records (D-079–D-083) covering grant architecture, NPC-to-NPC propagation, unprompted disclosure, NPC information boundaries MVP, contradiction detection pipeline
diff --git a/client/scenes/main.tscn b/client/scenes/main.tscn
index 0a866f02b..5362fca82 100644
--- a/client/scenes/main.tscn
+++ b/client/scenes/main.tscn
@@ -1,4 +1,4 @@
-[gd_scene load_steps=23 format=3 uid="uid://bswrmh7w8dbgm"]
+[gd_scene load_steps=24 format=3 uid="uid://bswrmh7w8dbgm"]
 
 [ext_resource type="Script" path="res://scripts/main.gd" id="1_main"]
 [ext_resource type="Script" path="res://scripts/rendering/world_renderer.gd" id="2_world"]
@@ -22,6 +22,7 @@
 [ext_resource type="PackedScene" path="res://ui/bug_report_dialog.tscn" id="19_bugreport"]
 [ext_resource type="PackedScene" path="res://ui/settings_dialog.tscn" id="21_settings"]
 [ext_resource type="Script" path="res://scripts/ui/debug_overlay.gd" id="22_debug"]
+[ext_resource type="PackedScene" path="res://ui/time_display.tscn" id="23_tdisplay"]
 
 [node name="Game" type="Node2D"]
 script = ExtResource("1_main")
@@ -118,6 +119,9 @@ zoom = Vector2(2, 2)
 [node name="InsertOverlay" type="CanvasLayer" parent="."]
 layer = 10
 
+; #263: Time display — diegetic insert clock, top-left placeholder (D-013, D-031)
+[node name="TimeDisplay" parent="InsertOverlay" instance=ExtResource("23_tdisplay")]
+
 ; InteractionPrompt — v0.1 fallback single-line "E - Talk" display
 [node name="InteractionPrompt" parent="InsertOverlay" instance=ExtResource("9_prompt")]
 
diff --git a/client/scripts/constants.gd b/client/scripts/constants.gd
index 5fc354777..31d4efa68 100644
--- a/client/scripts/constants.gd
+++ b/client/scripts/constants.gd
@@ -96,6 +96,11 @@ const FACING_INDICATOR_OFFSET: float = 14.0
 # two columns of text comfortably, leaves world game visible alongside.
 const DIALOGUE_MAX_WIDTH: int = 1200
 
+# D-031: Format game-minutes (0..1439) as station local time string "HH:MM".
+static func format_game_time(time_of_day: int) -> String:
+	var clamped: int = clampi(time_of_day, 0, 1439)
+	return "%02d:%02d" % [clamped / 60, clamped % 60]
+
 # Default camera zoom — used as fallback when get_camera_2d() returns null
 const CAMERA_DEFAULT_ZOOM: Vector2 = Vector2(2.0, 2.0)
 
diff --git a/client/scripts/main.gd b/client/scripts/main.gd
index 454c5fc44..9c68ba529 100644
--- a/client/scripts/main.gd
+++ b/client/scripts/main.gd
@@ -14,6 +14,7 @@ extends Node2D
 @onready var cursor_renderer = $UILayer/CursorRenderer  # D-056: z-layer 7
 @onready var gauntlet_hud = $UILayer/GauntletHUD  # #496: room timer + personal bests
 @onready var checklist_overlay = $UILayer/ChecklistOverlay  # #503: auto-checklist progress
+@onready var time_display = $InsertOverlay/TimeDisplay  # #263: diegetic time display (D-013, D-031)
 @onready var debug_overlay = $UILayer/DebugOverlay  # #511: F3 debug overlay
 @onready var bug_report_dialog = $ModalLayer/BugReportDialog  # #495: F12 WRONG button
 @onready var settings_dialog = $ModalLayer/SettingsDialog     # #528: audio settings (ESC/OPEN_MENU)
@@ -104,7 +105,7 @@ func _process(delta: float) -> void:
 		if interaction_list and interaction_list.has_method("update_from_state"):
 			if dialogue_box and dialogue_box.is_dialogue_active():
 				if interaction_list.is_showing():
-					interaction_list._hide()
+					interaction_list.hide_list()
 			else:
 				interaction_list.update_from_state()
 
@@ -131,6 +132,10 @@ func _process(delta: float) -> void:
 		if checklist_overlay and checklist_overlay.has_method("update_from_state"):
 			checklist_overlay.update_from_state()
 
+		# #263: Update time display (D-013, D-031)
+		if time_display and time_display.has_method("update_from_state"):
+			time_display.update_from_state()
+
 		# #511: Update debug overlay (F3 toggle, dev tool)
 		if debug_overlay and debug_overlay.has_method("update_from_state"):
 			debug_overlay.update_from_state()
diff --git a/client/tests/test_etalk_overlay_sprint17.gd b/client/tests/test_etalk_overlay_sprint17.gd
new file mode 100644
index 000000000..9446f662d
--- /dev/null
+++ b/client/tests/test_etalk_overlay_sprint17.gd
@@ -0,0 +1,298 @@
+## Sprint 17 — UX: E-Talk overlay improvement (#537) — Phase 1
+## Tests for relationship color indicator in interaction_list.gd.
+##
+## Spec refs:
+##   D-033 (entity color = relationship to player)
+##   D-051 (diegetic insert display — insert-only overlay)
+##   D-057 (interaction list, z-layer 6)
+##
+## Phase 1 scope (2026-02-24):
+##   Color bar only — NPC name and dialogue tier deferred to Phase 2 pending
+##   server protocol change (no known_attributes in wire protocol v13).
+##
+## Implementation: client/ui/interaction_list.gd
+##   `var _relationship_color: Color = Constants.IMPLANT_TEXT_DIM`
+##   `func _cache_entity_relationship() -> void`
+##   3px left-edge bar drawn in _draw() at 85% alpha, called from update_from_state()
+class_name TestETalkOverlaySprint17
+extends GdUnitTestSuite
+
+
+func before_test() -> void:
+	SimBridge.reset_test_state()
+	GameState.nearby_interactions = []
+	GameState.visible_entities = []
+	GameState.player_stance = ""
+
+
+func after_test() -> void:
+	GameState.nearby_interactions = []
+	GameState.visible_entities = []
+	GameState.player_stance = ""
+
+
+# -------------------------------------------------------------------------
+# D-033: Constants.color_for_relationship() — palette baseline (pure logic)
+# -------------------------------------------------------------------------
+
+func test_relationship_unknown_maps_to_teal() -> void:
+	assert_that(Constants.color_for_relationship("Unknown")).is_equal(Constants.ENTITY_COLOR_UNKNOWN)
+
+func test_relationship_friendly_maps_to_green() -> void:
+	assert_that(Constants.color_for_relationship("Friendly")).is_equal(Constants.ENTITY_COLOR_FRIENDLY)
+
+func test_relationship_poi_maps_to_amber() -> void:
+	assert_that(Constants.color_for_relationship("PersonOfInterest")).is_equal(Constants.ENTITY_COLOR_POI)
+
+func test_relationship_hostile_maps_to_red() -> void:
+	assert_that(Constants.color_for_relationship("Hostile")).is_equal(Constants.ENTITY_COLOR_HOSTILE)
+
+func test_relationship_known_falls_back_to_unknown_color() -> void:
+	# "Known" not matched in color_for_relationship() — falls through _ → ENTITY_COLOR_UNKNOWN
+	assert_that(Constants.color_for_relationship("Known")).is_equal(Constants.ENTITY_COLOR_UNKNOWN)
+
+func test_relationship_unknown_string_falls_back_to_unknown() -> void:
+	assert_that(Constants.color_for_relationship("SomeNewState")).is_equal(Constants.ENTITY_COLOR_UNKNOWN)
+
+
+# -------------------------------------------------------------------------
+# UIStrings: relationship state labels exist (Phase 2 pre-fixture)
+# -------------------------------------------------------------------------
+
+func test_ui_strings_has_relationship_unknown_label() -> void:
+	assert_that(UIStrings.has_key("relationship_states.unknown.label")).is_true()
+
+func test_ui_strings_has_relationship_known_label() -> void:
+	assert_that(UIStrings.has_key("relationship_states.known.label")).is_true()
+
+func test_ui_strings_has_relationship_friendly_label() -> void:
+	assert_that(UIStrings.has_key("relationship_states.friendly.label")).is_true()
+
+func test_ui_strings_has_relationship_poi_label() -> void:
+	assert_that(UIStrings.has_key("relationship_states.person_of_interest.label")).is_true()
+
+func test_ui_strings_has_relationship_hostile_label() -> void:
+	assert_that(UIStrings.has_key("relationship_states.hostile.label")).is_true()
+
+
+# -------------------------------------------------------------------------
+# _relationship_color initial state
+# -------------------------------------------------------------------------
+
+func test_relationship_color_default_is_implant_dim() -> void:
+	# Before any update, _relationship_color starts at IMPLANT_TEXT_DIM
+	var list = _make_list()
+	assert_that(list._relationship_color).is_equal(Constants.IMPLANT_TEXT_DIM)
+	list.queue_free()
+
+
+# -------------------------------------------------------------------------
+# _cache_entity_relationship(): D-033 palette via update_from_state() (#537 core)
+# -------------------------------------------------------------------------
+
+func test_cache_relationship_unknown_sets_unknown_color() -> void:
+	_setup_npc_interaction(2, "Unknown")
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_UNKNOWN)
+	list.queue_free()
+
+func test_cache_relationship_friendly_sets_green() -> void:
+	_setup_npc_interaction(2, "Friendly")
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_FRIENDLY)
+	list.queue_free()
+
+func test_cache_relationship_poi_sets_amber() -> void:
+	_setup_npc_interaction(2, "PersonOfInterest")
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_POI)
+	list.queue_free()
+
+func test_cache_relationship_hostile_sets_red() -> void:
+	_setup_npc_interaction(2, "Hostile")
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_HOSTILE)
+	list.queue_free()
+
+func test_cache_relationship_absent_field_uses_unknown_color() -> void:
+	# Entity present but "relationship" key missing → get("relationship", "Unknown") → Unknown color
+	GameState.visible_entities = [{
+		"entity_id": 2, "x": 12.0, "y": 9.0, "z": 0,
+		"kind": {"variant": "Npc", "data": null},
+		"visibility": "Forward",
+	}]
+	GameState.nearby_interactions = [{
+		"entity_id": 2, "entity_type": "Npc", "distance": 1,
+		"verbs": [{"kind": "Talk", "label": "Talk", "priority": 1, "available": true}],
+	}]
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_UNKNOWN)
+	list.queue_free()
+
+func test_cache_relationship_entity_not_in_visible_uses_dim_fallback() -> void:
+	# Entity in nearby_interactions but NOT in visible_entities → IMPLANT_TEXT_DIM fallback
+	GameState.visible_entities = []
+	GameState.nearby_interactions = [{
+		"entity_id": 2, "entity_type": "Npc", "distance": 1,
+		"verbs": [{"kind": "Talk", "label": "Talk", "priority": 1, "available": true}],
+	}]
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.IMPLANT_TEXT_DIM)
+	list.queue_free()
+
+func test_cache_relationship_updates_when_relationship_changes() -> void:
+	# First call: Unknown
+	_setup_npc_interaction(2, "Unknown")
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_UNKNOWN)
+
+	# Relationship shifts → re-cache picks up new value
+	_setup_npc_interaction(2, "Hostile")
+	list.update_from_state()
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_HOSTILE)
+	list.queue_free()
+
+func test_cache_relationship_targets_correct_entity_by_id() -> void:
+	# Two entities visible; nearby_interactions[0] is the target (entity 2, Friendly)
+	# Entity 3 (Hostile) must not pollute the color
+	GameState.visible_entities = [
+		{
+			"entity_id": 2, "x": 11.0, "y": 9.0, "z": 0,
+			"kind": {"variant": "Npc", "data": null},
+			"visibility": "Forward", "relationship": "Friendly", "observation": "Visible",
+		},
+		{
+			"entity_id": 3, "x": 12.0, "y": 9.0, "z": 0,
+			"kind": {"variant": "Npc", "data": null},
+			"visibility": "Forward", "relationship": "Hostile", "observation": "Visible",
+		},
+	]
+	GameState.nearby_interactions = [
+		{
+			"entity_id": 2, "entity_type": "Npc", "distance": 1,
+			"verbs": [{"kind": "Talk", "label": "Talk", "priority": 1, "available": true}],
+		},
+		{
+			"entity_id": 3, "entity_type": "Npc", "distance": 2,
+			"verbs": [{"kind": "Talk", "label": "Talk", "priority": 1, "available": true}],
+		},
+	]
+	var list = _make_list()
+	list.update_from_state()
+	# interaction[0] = entity 2 (Friendly) → green bar
+	assert_that(list._relationship_color).is_equal(Constants.ENTITY_COLOR_FRIENDLY)
+	list.queue_free()
+
+func test_z_layer_is_insert_canvas() -> void:
+	# D-049 / D-057: interaction list lives on InsertOverlay (CanvasLayer 10)
+	var list = _make_list()
+	assert_that(list.get_z_layer()).is_equal(Constants.CANVAS_INSERT)
+	list.queue_free()
+
+
+# -------------------------------------------------------------------------
+# Regression: interaction_list public API unaffected by #537 changes
+# -------------------------------------------------------------------------
+
+func test_list_hides_when_no_interactions() -> void:
+	GameState.nearby_interactions = []
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list.is_showing()).is_false()
+	list.queue_free()
+
+func test_list_shows_on_npc_interaction() -> void:
+	_setup_npc_interaction(2, "Unknown")
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list.is_showing()).is_true()
+	list.queue_free()
+
+func test_list_get_selected_verb_returns_first_verb() -> void:
+	GameState.nearby_interactions = [{
+		"entity_id": 2, "entity_type": "Npc", "distance": 1,
+		"verbs": [
+			{"kind": "Talk", "label": "Talk", "priority": 1, "available": true},
+			{"kind": "ExamineNpc", "label": "Look", "priority": 2, "available": true},
+		],
+	}]
+	var list = _make_list()
+	assert_that(list.get_selected_verb()).is_equal("Talk")
+	list.queue_free()
+
+func test_list_get_interaction_target_returns_entity_id() -> void:
+	GameState.visible_entities = [{
+		"entity_id": 5, "x": 12.0, "y": 9.0, "z": 0,
+		"kind": {"variant": "Npc", "data": null},
+		"visibility": "Forward", "relationship": "Unknown", "observation": "Visible",
+	}]
+	GameState.nearby_interactions = [{
+		"entity_id": 5, "entity_type": "Npc", "distance": 1,
+		"verbs": [{"kind": "Talk", "label": "Talk", "priority": 1, "available": true}],
+	}]
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list.get_interaction_target()).is_equal(5)
+	list.queue_free()
+
+func test_list_suppressed_when_insert_inactive() -> void:
+	_setup_npc_interaction(2, "Unknown")
+	var list = _make_list()
+	list.set_insert_active(false)
+	list.update_from_state()
+	assert_that(list.is_showing()).is_false()
+	list.queue_free()
+
+func test_list_hides_on_empty_verb_list() -> void:
+	GameState.nearby_interactions = [{
+		"entity_id": 2, "entity_type": "Npc", "distance": 1, "verbs": [],
+	}]
+	var list = _make_list()
+	list.update_from_state()
+	assert_that(list.is_showing()).is_false()
+	list.queue_free()
+
+
+# -------------------------------------------------------------------------
+# Phase 2 placeholders — deferred pending server protocol change (no known_attributes in v13)
+# -------------------------------------------------------------------------
+
+func skip_test_npc_name_displayed_when_known() -> void:
+	pass
+
+func skip_test_dialogue_tier_context_hint_for_friendly() -> void:
+	pass
+
+func skip_test_dialogue_tier_context_hint_for_hostile() -> void:
+	pass
+
+
+# -------------------------------------------------------------------------
+# Helpers
+# -------------------------------------------------------------------------
+
+func _make_list() -> Control:
+	var scene = load("res://ui/interaction_list.tscn")
+	var list = scene.instantiate()
+	add_child(list)  # _ready() fires here — @onready var _vbox resolves
+	return list
+
+
+## Set up GameState with a single NPC entity + matching interaction for tests.
+func _setup_npc_interaction(entity_id: int, relationship: String) -> void:
+	GameState.visible_entities = [{
+		"entity_id": entity_id, "x": 12.0, "y": 9.0, "z": 0,
+		"kind": {"variant": "Npc", "data": null},
+		"visibility": "Forward", "relationship": relationship, "observation": "Visible",
+	}]
+	GameState.nearby_interactions = [{
+		"entity_id": entity_id, "entity_type": "Npc", "distance": 1,
+		"verbs": [{"kind": "Talk", "label": "Talk", "priority": 1, "available": true}],
+	}]
diff --git a/client/tests/test_time_display_sprint17.gd b/client/tests/test_time_display_sprint17.gd
new file mode 100644
index 000000000..c19ca6a0e
--- /dev/null
+++ b/client/tests/test_time_display_sprint17.gd
@@ -0,0 +1,318 @@
+## Sprint 17 — Time display on insert HUD (#263)
+## Tests for Constants.format_game_time(), InsertClock wiring, and GameState integration.
+##
+## Spec refs:
+##   D-031 (game time: 10 ticks = 1 game-minute, 1440 min/day, HH:MM display)
+##   D-051 (diegetic insert display)
+##
+## Implementation: client/ui/time_display.gd — draw-based Control at InsertOverlay/TimeDisplay.
+## Format function: Constants.format_game_time(time_of_day: int) -> String (extracted for
+## testability from time_display.gd:46 inline Constants.format_game_time(tod)).
+##
+## Private state access: Tests read _time_str, _phase_str, _day_str, _has_data directly
+## because time_display.gd is draw-based (no Label nodes to inspect). This is an accepted
+## test pattern for draw-based UI — the private vars ARE the rendered output contract.
+## If the rendering approach changes (e.g. to Label nodes), these tests should switch to
+## reading Label.text via public node paths instead.
+class_name TestTimeDisplaySprint17
+extends GdUnitTestSuite
+
+var _clock: Control = null
+
+
+func before_test() -> void:
+	SimBridge.reset_test_state()
+	GameState.game_time = {}
+	var ClockScript = load("res://ui/time_display.gd")
+	_clock = Control.new()
+	_clock.set_script(ClockScript)
+	add_child(_clock)
+
+
+func after_test() -> void:
+	if _clock and is_instance_valid(_clock):
+		_clock.queue_free()
+		_clock = null
+	GameState.game_time = {}
+
+
+# -------------------------------------------------------------------------
+# Constants.format_game_time() — pure logic, D-031
+# -------------------------------------------------------------------------
+
+func test_format_midnight() -> void:
+	assert_that(Constants.format_game_time(0)).is_equal("00:00")
+
+func test_format_morning_start() -> void:
+	# 360 game-minutes = 6 h exactly (Morning phase boundary, D-031)
+	assert_that(Constants.format_game_time(360)).is_equal("06:00")
+
+func test_format_noon() -> void:
+	assert_that(Constants.format_game_time(720)).is_equal("12:00")
+
+func test_format_evening_start() -> void:
+	assert_that(Constants.format_game_time(1080)).is_equal("18:00")
+
+func test_format_end_of_day() -> void:
+	# Last valid minute — must not wrap or overflow
+	assert_that(Constants.format_game_time(1439)).is_equal("23:59")
+
+func test_format_pads_single_digit_hour() -> void:
+	# 30 min = 00:30
+	assert_that(Constants.format_game_time(30)).is_equal("00:30")
+
+func test_format_pads_single_digit_minute() -> void:
+	# 121 min = 02:01
+	assert_that(Constants.format_game_time(121)).is_equal("02:01")
+
+func test_format_half_past_hour() -> void:
+	assert_that(Constants.format_game_time(90)).is_equal("01:30")
+
+func test_format_arbitrary_midday() -> void:
+	# 835 min = 13:55
+	assert_that(Constants.format_game_time(835)).is_equal("13:55")
+
+
+# -------------------------------------------------------------------------
+# InsertClock initial state
+# -------------------------------------------------------------------------
+
+func test_insert_clock_initial_time_str_is_placeholder() -> void:
+	# Before any snapshot, _time_str must be "--:--" (not shown by _draw)
+	assert_that(_clock._time_str).is_equal("--:--")
+
+func test_insert_clock_initial_phase_str_is_empty() -> void:
+	assert_that(_clock._phase_str).is_equal("")
+
+func test_insert_clock_initial_day_str_is_empty() -> void:
+	assert_that(_clock._day_str).is_equal("")
+
+
+# -------------------------------------------------------------------------
+# InsertClock.update_from_state() — reads GameState.game_time
+# -------------------------------------------------------------------------
+
+func test_update_from_state_formats_time_str() -> void:
+	GameState.game_time = {
+		"day": 0, "time_of_day": 720, "day_phase": "Afternoon", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("12:00")
+
+func test_update_from_state_sets_phase_str() -> void:
+	GameState.game_time = {
+		"day": 0, "time_of_day": 1080, "day_phase": "Evening", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._phase_str).is_equal("Evening")
+
+func test_update_from_state_sets_day_str_one_indexed() -> void:
+	# Day 0 from server → "D1" display (1-indexed)
+	GameState.game_time = {
+		"day": 0, "time_of_day": 100, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._day_str).is_equal("D1")
+
+func test_update_from_state_day_2() -> void:
+	GameState.game_time = {
+		"day": 1, "time_of_day": 50, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._day_str).is_equal("D2")
+
+func test_update_from_state_midnight() -> void:
+	GameState.game_time = {
+		"day": 0, "time_of_day": 0, "day_phase": "Night", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("00:00")
+
+func test_update_from_state_end_of_day() -> void:
+	GameState.game_time = {
+		"day": 0, "time_of_day": 1439, "day_phase": "Night", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("23:59")
+
+func test_update_from_state_skips_empty_game_time() -> void:
+	# Empty game_time must not overwrite --:-- (guard in update_from_state)
+	GameState.game_time = {}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("--:--")
+
+func test_update_from_state_deduplicates_same_tick() -> void:
+	# Calling twice with identical data must produce same result (signature cache)
+	GameState.game_time = {
+		"day": 0, "time_of_day": 360, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("06:00")
+	# Call again — result unchanged, no crash
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("06:00")
+
+func test_update_from_state_updates_on_new_tick() -> void:
+	# time_of_day changes → signature changes → _time_str updates
+	GameState.game_time = {
+		"day": 0, "time_of_day": 60, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("01:00")
+
+	GameState.game_time = {
+		"day": 0, "time_of_day": 120, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._time_str).is_equal("02:00")
+
+
+# -------------------------------------------------------------------------
+# InsertClock.PHASE_COLORS — all four D-031 phases have colors
+# -------------------------------------------------------------------------
+
+func test_phase_colors_has_morning() -> void:
+	assert_that(_clock.PHASE_COLORS.has("Morning")).is_true()
+
+func test_phase_colors_has_afternoon() -> void:
+	assert_that(_clock.PHASE_COLORS.has("Afternoon")).is_true()
+
+func test_phase_colors_has_evening() -> void:
+	assert_that(_clock.PHASE_COLORS.has("Evening")).is_true()
+
+func test_phase_colors_has_night() -> void:
+	assert_that(_clock.PHASE_COLORS.has("Night")).is_true()
+
+func test_phase_color_applied_after_update() -> void:
+	GameState.game_time = {
+		"day": 0, "time_of_day": 100, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._phase_color).is_equal(_clock.PHASE_COLORS["Morning"])
+
+func test_phase_color_unknown_phase_uses_dim_fallback() -> void:
+	# Unknown phase string → Constants.IMPLANT_TEXT_DIM
+	GameState.game_time = {
+		"day": 0, "time_of_day": 100, "day_phase": "Twilight", "tick_rate": "Full",
+	}
+	_clock.update_from_state()
+	assert_that(_clock._phase_color).is_equal(Constants.IMPLANT_TEXT_DIM)
+
+
+# -------------------------------------------------------------------------
+# GameState: game_time field parsing (confirms apply_snapshot wiring)
+# -------------------------------------------------------------------------
+
+func test_game_time_populated_from_snapshot() -> void:
+	GameState.apply_snapshot({
+		"tick": 5, "entities": [],
+		"game_time": {
+			"day": 0, "time_of_day": 720, "day_phase": "Afternoon", "tick_rate": "Full",
+		},
+	})
+	assert_that(GameState.game_time.get("time_of_day")).is_equal(720)
+
+func test_game_time_all_four_phases_store_correctly() -> void:
+	for phase in ["Morning", "Afternoon", "Evening", "Night"]:
+		GameState.apply_snapshot({
+			"tick": 1, "entities": [],
+			"game_time": {
+				"day": 0, "time_of_day": 100, "day_phase": phase, "tick_rate": "Full",
+			},
+		})
+		assert_that(GameState.game_time.get("day_phase")).is_equal(phase)
+
+func test_game_time_missing_from_snapshot_preserves_previous() -> void:
+	GameState.game_time = {
+		"day": 0, "time_of_day": 360, "day_phase": "Morning", "tick_rate": "Full",
+	}
+	GameState.apply_snapshot({"tick": 2, "entities": []})
+	assert_that(GameState.game_time.get("time_of_day")).is_equal(360)
+
+func test_game_time_zero_time_of_day_stored() -> void:
+	# time_of_day = 0 (midnight) must not be treated as falsy/missing
+	GameState.apply_snapshot({
+		"tick": 1, "entities": [],
+		"game_time": {"day": 0, "time_of_day": 0, "day_phase": "Night", "tick_rate": "Full"},
+	})
+	assert_that(GameState.game_time.get("time_of_day")).is_equal(0)
+
+
+# -------------------------------------------------------------------------
+# SimBridge test mode: game_time fields are valid
+# -------------------------------------------------------------------------
+
+func test_sim_bridge_snapshot_has_game_time() -> void:
+	var snap = SimBridge._test_snapshot()
+	assert_that(snap.has("game_time")).is_true()
+	assert_that(snap.game_time is Dictionary).is_true()
+
+func test_sim_bridge_game_time_has_required_fields() -> void:
+	var snap = SimBridge._test_snapshot()
+	var gt: Dictionary = snap.game_time
+	assert_that(gt.has("day")).is_true()
+	assert_that(gt.has("time_of_day")).is_true()
+	assert_that(gt.has("day_phase")).is_true()
+	assert_that(gt.has("tick_rate")).is_true()
+
+func test_sim_bridge_time_of_day_is_non_negative() -> void:
+	var snap = SimBridge._test_snapshot()
+	assert_that(snap.game_time.get("time_of_day", -1) as int).is_greater_equal(0)
+
+func test_sim_bridge_time_of_day_within_day_bounds() -> void:
+	# D-031: 1440 game-minutes per day, valid range 0..1439
+	var snap = SimBridge._test_snapshot()
+	assert_that(snap.game_time.get("time_of_day", 0) as int).is_less_equal(1439)
+
+func test_sim_bridge_day_phase_is_valid() -> void:
+	var snap = SimBridge._test_snapshot()
+	var phase: String = snap.game_time.get("day_phase", "")
+	assert_that(["Morning", "Afternoon", "Evening", "Night"].has(phase)).is_true()
+
+
+# -------------------------------------------------------------------------
+# Scene: InsertClock node at InsertOverlay/TimeDisplay
+# -------------------------------------------------------------------------
+
+func test_insert_clock_exists_in_ui_layer() -> void:
+	var scene := load("res://scenes/main.tscn")
+	var instance = scene.instantiate()
+	auto_free(instance)
+	add_child(instance)
+
+	assert_that(instance.get_node_or_null("InsertOverlay/TimeDisplay")).is_not_null()
+
+func test_insert_clock_time_str_updates_after_process() -> void:
+	var scene := load("res://scenes/main.tscn")
+	var instance = scene.instantiate()
+	auto_free(instance)
+	add_child(instance)
+
+	GameState.apply_snapshot({
+		"tick": 1, "version": Protocol.PROTOCOL_VERSION, "entities": [],
+		"game_time": {"day": 0, "time_of_day": 720, "day_phase": "Afternoon", "tick_rate": "Full"},
+	})
+	instance._process(0.016)
+
+	var clock = instance.get_node_or_null("InsertOverlay/TimeDisplay")
+	assert_that(clock).is_not_null()
+	assert_that(clock._time_str).is_equal("12:00")
+
+
+# -------------------------------------------------------------------------
+# Regression: debug_overlay still reads game_time correctly (#511)
+# -------------------------------------------------------------------------
+
+func test_debug_overlay_reads_game_time_day_phase() -> void:
+	GameState.apply_snapshot({
+		"tick": 1, "entities": [],
+		"game_time": {"day": 0, "time_of_day": 100, "day_phase": "Morning", "tick_rate": "Full"},
+	})
+	assert_that(GameState.game_time.get("day_phase")).is_equal("Morning")
+
+func test_debug_overlay_reads_game_time_tick_rate() -> void:
+	GameState.apply_snapshot({
+		"tick": 1, "entities": [],
+		"game_time": {"day": 0, "time_of_day": 100, "day_phase": "Morning", "tick_rate": "Half"},
+	})
+	assert_that(GameState.game_time.get("tick_rate")).is_equal("Half")
diff --git a/client/ui/interaction_list.gd b/client/ui/interaction_list.gd
index 2a96d6850..94c099bc9 100644
--- a/client/ui/interaction_list.gd
+++ b/client/ui/interaction_list.gd
@@ -29,6 +29,8 @@ var _verb_items: Array = []  # sorted [{kind, label, priority, available}]
 var _selected_index: int = 0
 var _active_tween: Tween = null
 var _verb_labels: Array[Label] = []
+# #537: D-033 relationship color — cached per target, drawn as left-edge accent bar
+var _relationship_color: Color = Constants.IMPLANT_TEXT_DIM
 
 @onready var _vbox: VBoxContainer = $VBox
 
@@ -39,10 +41,14 @@ func _ready() -> void:
 	mouse_filter = Control.MOUSE_FILTER_IGNORE
 
 
+var _last_screen_pos: Vector2 = Vector2.ZERO
+
 func _process(_delta: float) -> void:
 	if _showing:
 		_update_screen_position()
-		queue_redraw()
+		if position != _last_screen_pos:
+			_last_screen_pos = position
+			queue_redraw()
 
 
 func _draw() -> void:
@@ -52,6 +58,9 @@ func _draw() -> void:
 	var bg_rect := Rect2(-pad, -pad, size.x + pad * 2, size.y + pad * 2)
 	draw_rect(bg_rect, INSERT_BG)
 	draw_rect(bg_rect, Constants.IMPLANT_TEXT_DIM * Color(1, 1, 1, 0.3), false, 1.0)
+	# #537: D-033 relationship color accent — 3px left-edge bar signals NPC relationship
+	var bar_rect := Rect2(-pad, -pad, 3.0, bg_rect.size.y)
+	draw_rect(bar_rect, _relationship_color * Color(1, 1, 1, 0.85))
 
 
 func update_from_state() -> void:
@@ -88,6 +97,7 @@ func update_from_state() -> void:
 	_verb_items = sorted
 	_selected_index = 0
 	_cache_entity_position()
+	_cache_entity_relationship()
 	_rebuild_labels()
 	_show()
 
@@ -127,6 +137,17 @@ func _cache_entity_position() -> void:
 			return
 
 
+## #537: Cache relationship color for the target entity (D-033 palette).
+## Falls back to IMPLANT_TEXT_DIM for non-NPC or unknown entities.
+func _cache_entity_relationship() -> void:
+	for entity in GameState.visible_entities:
+		if entity.get("entity_id") == _current_target_id:
+			var rel: String = str(entity.get("relationship", "Unknown"))
+			_relationship_color = Constants.color_for_relationship(rel)
+			return
+	_relationship_color = Constants.IMPLANT_TEXT_DIM
+
+
 ## Convert entity world position to screen coords and reposition this Control.
 ## Runs every frame while showing so the list tracks the entity as the camera moves.
 func _update_screen_position() -> void:
@@ -187,6 +208,10 @@ func get_visible_verb_count() -> int:
 	return _verb_items.size()
 
 
+func hide_list() -> void:
+	_hide()
+
+
 func is_showing() -> bool:
 	return _showing
 
diff --git a/client/ui/time_display.gd b/client/ui/time_display.gd
new file mode 100644
index 000000000..bf1fe44ee
--- /dev/null
+++ b/client/ui/time_display.gd
@@ -0,0 +1,97 @@
+extends Control
+
+## #263: Time display — diegetic time readout on the player's neural insert (D-013, D-031).
+## Shows station local time (HH:MM), day phase, and day number.
+## Lives on InsertOverlay (CanvasLayer 10) per D-051 diegetic insert principle.
+## Draw-based for implant visual aesthetic. Updated via update_from_state() from main.gd.
+##
+## Placeholder layout — position and style will be refined when #314 wireframe lands.
+
+const FONT_SIZE_TIME: int = 15
+const FONT_SIZE_META: int = 10
+const PADDING := Vector2(10, 7)
+const BG_COLOR := Color(0.04, 0.05, 0.08, 0.70)
+const BORDER_COLOR := Color(0.10, 0.20, 0.26, 0.65)
+
+# Day phase colors — station lighting cycle (D-031)
+const PHASE_COLORS := {
+	"Morning":   Color("#aed6dc"),   # pale cyan-blue — early light
+	"Afternoon": Color("#E0F7FA"),   # bright cyan-white — full day
+	"Evening":   Color("#9EBFC4"),   # dimmed — dusk transition
+	"Night":     Color("#4a7080"),   # dark teal — station nightwatch
+}
+
+var _time_str: String = "--:--"
+var _phase_str: String = ""
+var _day_str: String = ""
+var _day_text: String = ""
+var _phase_color: Color = Constants.IMPLANT_TEXT_DIM
+var _last_signature: String = ""
+var _has_data: bool = false
+
+# Cached geometry — recomputed in update_from_state(), used in _draw()
+var _time_size: Vector2 = Vector2.ZERO
+var _phase_size: Vector2 = Vector2.ZERO
+var _day_size: Vector2 = Vector2.ZERO
+var _meta_h: float = 0.0
+var _box_w: float = 0.0
+var _box_h: float = 0.0
+
+
+func _ready() -> void:
+	mouse_filter = Control.MOUSE_FILTER_IGNORE
+
+
+func update_from_state() -> void:
+	var gt: Dictionary = GameState.game_time
+	if gt.is_empty():
+		return
+	var tod: int = int(gt.get("time_of_day", 0))
+	var day: int = int(gt.get("day", 0))
+	var phase: String = str(gt.get("day_phase", ""))
+	var sig: String = "%d:%d:%s" % [tod, day, phase]
+	if sig == _last_signature:
+		return
+	_last_signature = sig
+	_time_str = Constants.format_game_time(tod)
+	_phase_str = phase
+	_day_str = "D%d" % (day + 1)
+	_day_text = "  " + _day_str
+	_phase_color = PHASE_COLORS.get(phase, Constants.IMPLANT_TEXT_DIM)
+	_has_data = true
+	_cache_geometry()
+	queue_redraw()
+
+
+func _cache_geometry() -> void:
+	var font := ThemeDB.fallback_font
+	_time_size = font.get_string_size(_time_str, HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_TIME)
+	_phase_size = font.get_string_size(_phase_str, HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_META)
+	_day_size = font.get_string_size(_day_text, HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_META)
+	_meta_h = font.get_string_size("A", HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_META).y
+	var meta_w := _phase_size.x + _day_size.x
+	var content_w := max(_time_size.x, meta_w)
+	_box_w = content_w + PADDING.x * 2
+	_box_h = PADDING.y * 2 + _time_size.y + 3 + _meta_h
+
+
+func _draw() -> void:
+	if not _has_data:
+		return
+
+	# Background
+	draw_rect(Rect2(Vector2.ZERO, Vector2(_box_w, _box_h)), BG_COLOR)
+	draw_rect(Rect2(Vector2.ZERO, Vector2(_box_w, _box_h)), BORDER_COLOR, false, 1.0)
+
+	var font := ThemeDB.fallback_font
+
+	# HH:MM (primary, full brightness)
+	draw_string(font, Vector2(PADDING.x, PADDING.y + _time_size.y),
+		_time_str, HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_TIME, Constants.IMPLANT_TEXT_COLOR)
+
+	# Phase + day number (secondary, dimmed + phase-tinted)
+	var meta_y := PADDING.y + _time_size.y + 3 + _meta_h
+	draw_string(font, Vector2(PADDING.x, meta_y),
+		_phase_str, HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_META, _phase_color)
+	draw_string(font, Vector2(PADDING.x + _phase_size.x, meta_y),
+		_day_text, HORIZONTAL_ALIGNMENT_LEFT, -1, FONT_SIZE_META, Constants.IMPLANT_TEXT_DIM)
diff --git a/client/ui/time_display.tscn b/client/ui/time_display.tscn
new file mode 100644
index 000000000..7145a5abb
--- /dev/null
+++ b/client/ui/time_display.tscn
@@ -0,0 +1,22 @@
+[gd_scene load_steps=2 format=3 uid="uid://b4timedisplay1"]
+
+[ext_resource type="Script" path="res://ui/time_display.gd" id="1_tdisplay"]
+
+; #263: Time display — top-left placeholder per D-013/D-051.
+; Position and size will be refined when #314 wireframe lands.
+; NOTE: draw-based content manages its own layout; Control rect is a
+; minimum bounding box, not a clip rect. Increase if content grows.
+[node name="TimeDisplay" type="Control"]
+anchors_preset = 0
+anchor_left = 0.0
+anchor_top = 0.0
+anchor_right = 0.0
+anchor_bottom = 0.0
+offset_left = 16.0
+offset_top = 16.0
+offset_right = 200.0
+offset_bottom = 70.0
+grow_horizontal = 2
+grow_vertical = 2
+mouse_filter = 2
+script = ExtResource("1_tdisplay")