diff --git a/backend/app/routers/auth.py b/backend/app/routers/auth.py
index b1e1dd5..b5afe97 100644
--- a/backend/app/routers/auth.py
+++ b/backend/app/routers/auth.py
@@ -21,6 +21,9 @@ pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
 
 router = APIRouter()
 
+## Minimum age to register. This platform is adults-only.
+MIN_AGE = 18
+
 
 # --- Pydantic schemas ---
 
@@ -39,14 +42,19 @@ class RegisterRequest(BaseModel):
     username: str
     email: EmailStr
     password: str
-    over_18: bool  # Simple boolean confirmation instead of date_of_birth
+    # Real date of birth -- the server computes age from it and rejects
+    # anyone under MIN_AGE. Still self-attested (no document check yet), but
+    # a concrete, stored, legally-meaningful data point rather than a
+    # throwaway checkbox, and the seam for a future hard ID-verification
+    # pass. See docs/architecture/content_moderation.md 5.2.
+    date_of_birth: date
 
 
 class UserResponse(BaseModel):
     id: int
     username: str
     email: str
-    date_of_birth: str | None = None
+    date_of_birth: date | None = None
     is_active: bool
     created_at: datetime | None = None
 
@@ -108,15 +116,9 @@ def hash_password(password: str) -> str:
 def calculate_age(birth_date: date, today: date | None = None) -> int:
     """Calculate age in years from a birth date.
 
-    Not called by /register anymore (that endpoint now just trusts the
-    client's over_18 boolean, see RegisterRequest) -- kept as a real,
-    tested utility since date-of-birth storage/verification is coming
-    back in a future pass (real age math, not just a client-side claim,
-    the user explicitly wants to revisit this design). Removing it broke
-    backend/tests/test_auth_age_gate.py's collection entirely (ImportError
-    on `from app.routers.auth import calculate_age`) for zero benefit --
-    restoring it is the lower-risk path over rewriting or deleting 17
-    tests for logic this codebase will need again.
+    Used by /register (PC3 Phase 3) to compute age from the submitted
+    date_of_birth and enforce the 18+ gate. See
+    docs/architecture/content_moderation.md 5.2.
 
     Args:
         birth_date: The person's date of birth.
@@ -155,12 +157,20 @@ def _issue_refresh_token(user_id: int, db: AsyncSession) -> str:
 async def register(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
     """Register a new user and return access + refresh tokens.
 
-    Requires over_18 boolean confirmation; rejects users who are not 18+.
+    Requires a date of birth; the server computes age and rejects anyone
+    under MIN_AGE (18). See docs/architecture/content_moderation.md for the
+    verification design and its self-attestation limitation.
     """
-    if not req.over_18:
+    age = calculate_age(req.date_of_birth)
+    if age < 0 or req.date_of_birth > date.today():
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
-            detail="Must be 18 or older to register",
+            detail="Invalid date of birth",
+        )
+    if age < MIN_AGE:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail=f"You must be at least {MIN_AGE} to use this platform",
         )
 
     # Check if username already exists
@@ -183,7 +193,7 @@ async def register(req: RegisterRequest, db: AsyncSession = Depends(get_db)):
         username=req.username,
         email=req.email,
         hashed_password=hash_password(req.password),
-        date_of_birth=None,  # No longer collecting DOB
+        date_of_birth=req.date_of_birth,
     )
     db.add(user)
     await db.flush()  # flush to get user.id before creating refresh token
diff --git a/backend/tests/test_auth_age_gate.py b/backend/tests/test_auth_age_gate.py
index 3b372b9..264c7f4 100644
--- a/backend/tests/test_auth_age_gate.py
+++ b/backend/tests/test_auth_age_gate.py
@@ -3,92 +3,102 @@
 from datetime import date, timedelta
 
 import pytest
+from fastapi.testclient import TestClient
 
-from app.routers.auth import calculate_age
+from app.main import app
+from app.routers.auth import calculate_age, MIN_AGE, RegisterRequest
 
 
 class TestCalculateAge:
     """Unit tests for the calculate_age helper."""
 
     def test_exactly_18(self):
-        """A person born exactly 18 years ago today is 18."""
-        today = date(2025, 6, 15)
+        today = date(2026, 6, 15)
         dob = today.replace(year=today.year - 18)
         assert calculate_age(dob, today=today) == 18
 
     def test_just_turned_18(self):
-        """A person who turned 18 yesterday is 18."""
-        today = date(2025, 6, 15)
+        today = date(2026, 6, 15)
         dob = today.replace(year=today.year - 18) - timedelta(days=1)
         assert calculate_age(dob, today=today) == 18
 
     def test_one_day_short_of_18(self):
-        """A person born one day after their 18th birthday is 17."""
-        today = date(2025, 6, 15)
+        today = date(2026, 6, 15)
         dob = today.replace(year=today.year - 18) + timedelta(days=1)
         assert calculate_age(dob, today=today) == 17
 
-    def test_17_years_old(self):
-        """A person who is 17 years old today is 17."""
-        today = date(2025, 6, 15)
-        dob = date(2008, 6, 15)
-        assert calculate_age(dob, today=today) == 17
+    def test_leap_day_birthday_before(self):
+        assert calculate_age(date(2000, 2, 29), today=date(2024, 2, 28)) == 23
 
-    def test_65_years_old(self):
-        """A person who is 65 is correctly calculated."""
-        today = date(2025, 6, 15)
-        dob = today.replace(year=today.year - 65)
-        assert calculate_age(dob, today=today) == 65
-
-    def test_newborn(self):
-        """A newborn is 0."""
-        today = date(2025, 6, 15)
-        dob = today
-        assert calculate_age(dob, today=today) == 0
-
-    def test_birthday_not_yet_this_year(self):
-        """Person born Dec 31, 2000 — on Jan 1, 2025 they are still 24."""
-        dob = date(2000, 12, 31)
-        assert calculate_age(dob, today=date(2025, 1, 1)) == 24
-
-    def test_birthday_today(self):
-        """Person born Dec 31, 2000 — on Dec 31, 2024 they turn 24."""
-        dob = date(2000, 12, 31)
-        assert calculate_age(dob, today=date(2024, 12, 31)) == 24
+    def test_leap_day_birthday_after(self):
+        assert calculate_age(date(2000, 2, 29), today=date(2024, 3, 1)) == 24
 
 
-class TestRegisterRequestOver18Field:
-    """Tests for RegisterRequest's over_18 field.
+class TestRegisterRequestDob:
+    def test_dob_parsed_from_iso_string(self):
+        req = RegisterRequest(username="u", email="u@example.com", password="p",
+                              date_of_birth="1990-01-01")
+        assert req.date_of_birth == date(1990, 1, 1)
 
-    Replaces TestRegisterRequestDateValidation -- date_of_birth and its
-    field_validator were removed from RegisterRequest 2026-08-20 (interim
-    simplification: a plain client-side over_18 confirmation instead of
-    collecting/validating an actual date of birth; see calculate_age's
-    own docstring in app/routers/auth.py for why that function is still
-    here even though this endpoint no longer calls it). There's no date
-    format left to validate, so the equivalent coverage is just: the
-    field exists, is a real bool, and is required."""
-
-    def test_over_18_true_accepted(self):
-        from app.routers.auth import RegisterRequest
-
-        req = RegisterRequest(username="u", email="u@example.com", password="p", over_18=True)
-        assert req.over_18 is True
-
-    def test_over_18_false_accepted(self):
-        """False is a valid value at the schema level -- the endpoint,
-        not the schema, is what rejects it (see
-        TestRegister::test_register_rejects_not_over_18 in
-        test_auth_endpoints.py)."""
-        from app.routers.auth import RegisterRequest
-
-        req = RegisterRequest(username="u", email="u@example.com", password="p", over_18=False)
-        assert req.over_18 is False
-
-    def test_over_18_missing_rejected(self):
-        """over_18 has no default -- omitting it entirely is a validation error."""
-        from app.routers.auth import RegisterRequest
-        from pydantic import ValidationError
-
-        with pytest.raises(ValidationError):
+    def test_dob_required(self):
+        with pytest.raises(Exception):
             RegisterRequest(username="u", email="u@example.com", password="p")
+
+    def test_bad_dob_string_rejected(self):
+        with pytest.raises(Exception):
+            RegisterRequest(username="u", email="u@example.com", password="p",
+                            date_of_birth="not-a-date")
+
+
+class TestRegisterAgeGate:
+    """End-to-end: the /register endpoint computes age from the DOB."""
+
+    def _dob_for_age(self, years: int) -> str:
+        return (date.today().replace(year=date.today().year - years)).isoformat()
+
+    def test_adult_accepted(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_adult", "email": "gate_adult@e.com",
+            "password": "secret123", "date_of_birth": self._dob_for_age(25),
+        })
+        assert r.status_code == 201, r.text
+
+    def test_minor_rejected(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_minor", "email": "gate_minor@e.com",
+            "password": "secret123", "date_of_birth": self._dob_for_age(15),
+        })
+        assert r.status_code == 403
+        assert str(MIN_AGE) in r.json()["detail"]
+
+    def test_exactly_18_accepted(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_18", "email": "gate_18@e.com",
+            "password": "secret123",
+            "date_of_birth": (date.today().replace(year=date.today().year - 18) - timedelta(days=1)).isoformat(),
+        })
+        assert r.status_code == 201, r.text
+
+    def test_future_dob_rejected(self):
+        client = TestClient(app)
+        r = client.post("/api/auth/register", json={
+            "username": "gate_future", "email": "gate_future@e.com",
+            "password": "secret123", "date_of_birth": "2999-01-01",
+        })
+        assert r.status_code == 400
+
+    def test_dob_is_stored(self):
+        client = TestClient(app)
+        dob = self._dob_for_age(30)
+        reg = client.post("/api/auth/register", json={
+            "username": "gate_stored", "email": "gate_stored@e.com",
+            "password": "secret123", "date_of_birth": dob,
+        })
+        assert reg.status_code == 201
+        me = client.get("/api/auth/me", headers={
+            "Authorization": f"Bearer {reg.json()['access_token']}"
+        })
+        assert me.json()["date_of_birth"] == dob
diff --git a/backend/tests/test_auth_endpoints.py b/backend/tests/test_auth_endpoints.py
index afe949e..9305bb7 100644
--- a/backend/tests/test_auth_endpoints.py
+++ b/backend/tests/test_auth_endpoints.py
@@ -73,7 +73,7 @@ class TestRegister:
                 "username": "newuser",
                 "email": "new@example.com",
                 "password": "secret123",
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         assert resp.status_code == 201
@@ -81,26 +81,23 @@ class TestRegister:
         assert "access_token" in data
         assert data["token_type"] == "bearer"
 
-    def test_register_rejects_not_over_18(self):
-        """over_18=false gets a 400 with a detail message.
-
-        The interim design (2026-08-20) trusts a client-side boolean
-        confirmation instead of collecting/validating an actual date of
-        birth -- this only checks that the flag is respected, not real
-        age math (there's no date to verify against anymore). Real DOB
-        collection/verification may come back in a future pass."""
+    def test_register_rejects_under_18(self):
+        """A DOB that computes to under 18 gets a 403 (see test_auth_age_gate
+        for the age-math coverage)."""
+        from datetime import date
         client = TestClient(app)
+        minor_dob = date.today().replace(year=date.today().year - 14).isoformat()
         resp = client.post(
             "/api/auth/register",
             json={
                 "username": "kid",
                 "email": "kid@example.com",
                 "password": "secret123",
-                "over_18": False,
+                "date_of_birth": minor_dob,
             },
         )
-        assert resp.status_code == 400
-        assert "18 or older" in resp.json()["detail"]
+        assert resp.status_code == 403
+        assert "at least 18" in resp.json()["detail"]
 
     def test_register_rejects_duplicate_username(self):
         """Registering the same username twice returns 409."""
@@ -112,7 +109,7 @@ class TestRegister:
                 "username": "duplicate",
                 "email": "dup1@example.com",
                 "password": "secret123",
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         # Second registration with same username, different email
@@ -122,7 +119,7 @@ class TestRegister:
                 "username": "duplicate",
                 "email": "dup2@example.com",
                 "password": "secret123",
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         assert resp.status_code == 409
@@ -137,7 +134,7 @@ class TestRegister:
                 "username": "user1",
                 "email": "same@example.com",
                 "password": "secret123",
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         resp = client.post(
@@ -146,19 +143,14 @@ class TestRegister:
                 "username": "user2",
                 "email": "same@example.com",
                 "password": "secret123",
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         assert resp.status_code == 409
         assert "Email already registered" in resp.json()["detail"]
 
-    def test_register_missing_over_18(self):
-        """Missing the required over_18 field returns 422.
-
-        Replaces the old test_register_invalid_date_format -- there's no
-        date format to get wrong anymore (no date field at all), so the
-        closest equivalent "malformed request" case is the required
-        over_18 boolean being absent entirely."""
+    def test_register_missing_dob(self):
+        """Missing the required date_of_birth field returns 422."""
         client = TestClient(app)
         resp = client.post(
             "/api/auth/register",
@@ -189,7 +181,7 @@ class TestLogin:
                 "username": username,
                 "email": email,
                 "password": password,
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         assert resp.status_code == 201
diff --git a/backend/tests/test_auth_expired_token.py b/backend/tests/test_auth_expired_token.py
index 960afb6..25f919e 100644
--- a/backend/tests/test_auth_expired_token.py
+++ b/backend/tests/test_auth_expired_token.py
@@ -93,7 +93,7 @@ def _register_user(client: TestClient, username: str) -> str:
             "username": username,
             "email": f"{username}@example.com",
             "password": "secret123",
-            "over_18": True,
+            "date_of_birth": "1990-01-01",
         },
     )
     assert resp.status_code == 201
diff --git a/backend/tests/test_avatar_loadout.py b/backend/tests/test_avatar_loadout.py
index 3090917..d4944b7 100644
--- a/backend/tests/test_avatar_loadout.py
+++ b/backend/tests/test_avatar_loadout.py
@@ -18,7 +18,7 @@ def _auth_headers(client: TestClient, username: str) -> dict:
             "username": username,
             "email": f"{username}@example.com",
             "password": "secret123",
-            "over_18": True,
+            "date_of_birth": "1990-01-01",
         },
     )
     assert resp.status_code == 201, resp.text
diff --git a/backend/tests/test_refresh_endpoint.py b/backend/tests/test_refresh_endpoint.py
index 3da8e47..7c66001 100644
--- a/backend/tests/test_refresh_endpoint.py
+++ b/backend/tests/test_refresh_endpoint.py
@@ -59,7 +59,7 @@ class TestRefresh:
                 "username": username,
                 "email": email,
                 "password": password,
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         assert resp.status_code == 201
@@ -143,7 +143,7 @@ class TestRefresh:
                 "username": "refep_loginrefuser",
                 "email": "loginref@example.com",
                 "password": "secret123",
-                "over_18": True,
+                "date_of_birth": "1990-01-01",
             },
         )
         # Login to get a refresh token
diff --git a/backend/tests/test_world_join.py b/backend/tests/test_world_join.py
index 6ca32d5..566dc40 100644
--- a/backend/tests/test_world_join.py
+++ b/backend/tests/test_world_join.py
@@ -13,7 +13,7 @@ from app.main import app
 
 def _auth(client: TestClient, name: str) -> tuple[dict, int]:
     r = client.post("/api/auth/register", json={
-        "username": name, "email": f"{name}@e.com", "password": "secret123", "over_18": True,
+        "username": name, "email": f"{name}@e.com", "password": "secret123", "date_of_birth": "1990-01-01",
     })
     assert r.status_code == 201, r.text
     headers = {"Authorization": f"Bearer {r.json()['access_token']}"}
diff --git a/docs/architecture/content_moderation.md b/docs/architecture/content_moderation.md
index 66f5ae0..d5c7952 100644
--- a/docs/architecture/content_moderation.md
+++ b/docs/architecture/content_moderation.md
@@ -227,18 +227,33 @@ An account has an **age verification status**:
 
 ### 5.2 Tier 1 — Self-Declaration Flow
 
+> **Implemented, PC3 Phase 3.** `POST /api/auth/register` now takes a real
+> `date_of_birth` (ISO `YYYY-MM-DD`), not the throwaway `over_18` boolean it
+> had before. The server computes age (`auth.calculate_age`) and rejects
+> anyone under `auth.MIN_AGE` (18) with a **403** — this platform is
+> adults-only, so there is no "minor, restricted" tier here (the 13+ rows
+> below are the general design, not the current gate). A future-in-the-past
+> or nonsensical date is a **400**. The DOB is stored on the user row and
+> surfaced only back to that user (`/api/auth/me`), never to other players.
+>
+> **Limitation, stated plainly:** this is still self-attested — a determined
+> user can enter a false DOB. It is a concrete, stored, legally-meaningful
+> data point (matching how most platforms gate before adding hard checks)
+> and the seam for Tier 2. Encryption-at-rest for the DOB column and the
+> Tier 2 ID-check hook below are **not yet implemented**.
+
 ```
 User submits { date_of_birth }
         │
         ▼
-Server validates format & plausibility (age 13–120, not in future)
+Server validates format & plausibility (real date, not in future)
         │
         ▼
 Compute age from DOB
         │
         ▼
-age >= 18 ──► status = self_declared (adult)
-age >= 13 ──► status = self_declared (minor, restricted)
+age >= 18 ──► status = self_declared (adult)   ← the current gate
+age >= 13 ──► status = self_declared (minor, restricted)   ← design only
 age <  13 ──► status = rejected (below minimum platform age)
 ```
 
diff --git a/scenes/main_menu.tscn b/scenes/main_menu.tscn
index 65b3cac..550c2fa 100644
--- a/scenes/main_menu.tscn
+++ b/scenes/main_menu.tscn
@@ -83,11 +83,11 @@ visible = false
 placeholder_text = "Email"
 size_flags_horizontal = 3
 
-[node name="Over18Check" type="CheckBox" parent="CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox"]
+[node name="DobEdit" type="LineEdit" parent="CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox"]
 layout_mode = 1
 visible = false
-text = "I am 18 or older"
 size_flags_horizontal = 3
+placeholder_text = "Date of birth (YYYY-MM-DD)"
 
 [node name="AuthButton" type="Button" parent="CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox"]
 layout_mode = 1
diff --git a/scripts/api_client.gd b/scripts/api_client.gd
index 99c8f8b..f9efc33 100644
--- a/scripts/api_client.gd
+++ b/scripts/api_client.gd
@@ -178,18 +178,19 @@ func login(username: String, password: String) -> Dictionary:
 
 
 ## Register a new user. On success stores the returned access token.
-## @param over_18 Must be true; the backend rejects registration otherwise.
+## @param date_of_birth ISO "YYYY-MM-DD". The backend computes age from it
+##                       and rejects under-18s (403).
 func register(
 	username: String,
 	email: String,
 	password: String,
-	over_18: bool
+	date_of_birth: String
 ) -> Dictionary:
 	var payload := {
 		"username": username,
 		"email": email,
 		"password": password,
-		"over_18": over_18,
+		"date_of_birth": date_of_birth,
 	}
 	var result := await request(
 		HTTPClient.METHOD_POST,
diff --git a/scripts/main_menu.gd b/scripts/main_menu.gd
index 824411d..617623c 100644
--- a/scripts/main_menu.gd
+++ b/scripts/main_menu.gd
@@ -35,7 +35,7 @@ var _auth_mode_label: Label
 var _username_edit: LineEdit
 var _password_edit: LineEdit
 var _email_edit: LineEdit
-var _over_18_check: CheckBox
+var _dob_edit: LineEdit
 var _auth_button: Button
 var _status_label: Label
 var _welcome_label: Label
@@ -59,7 +59,7 @@ func _ready() -> void:
 	_username_edit = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/UsernameEdit
 	_password_edit = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/PasswordEdit
 	_email_edit = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/EmailEdit
-	_over_18_check = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/Over18Check
+	_dob_edit = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/DobEdit
 	_auth_button = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/AuthButton
 	_status_label = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/AuthStatusLabel
 	_welcome_label = $CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/WelcomeLabel
@@ -115,7 +115,7 @@ func _show_authenticated(username: String) -> void:
 	_username_edit.visible = false
 	_password_edit.visible = false
 	_email_edit.visible = false
-	_over_18_check.visible = false
+	_dob_edit.visible = false
 	_auth_button.visible = false
 	_auth_mode_label.visible = false
 	_play_button.disabled = false
@@ -131,8 +131,8 @@ func _reset_to_logged_out() -> void:
 	_status_label.visible = false
 	_welcome_label.visible = false
 	_email_edit.visible = false
-	_over_18_check.visible = false
-	_over_18_check.button_pressed = false
+	_dob_edit.visible = false
+	_dob_edit.text = ""
 	_play_button.disabled = true  # Gate play behind successful auth.
 	_customize_button.disabled = true
 	_update_auth_mode_ui()
@@ -158,6 +158,19 @@ func _on_quit_button_pressed() -> void:
 	get_tree().quit()
 
 
+## Loose client-side check -- YYYY-MM-DD, a real calendar date, not in the
+## future. The backend does the authoritative age computation.
+func _is_valid_dob(dob: String) -> bool:
+	var m := RegEx.new()
+	m.compile("^\\d{4}-\\d{2}-\\d{2}$")
+	if m.search(dob) == null:
+		return false
+	var parts := dob.split("-")
+	var d := {"year": int(parts[0]), "month": int(parts[1]), "day": int(parts[2]), "hour": 0, "minute": 0, "second": 0}
+	var unix := Time.get_unix_time_from_datetime_dict(d)
+	return unix > 0 and unix < Time.get_unix_time_from_system()
+
+
 # ─── Auth panel toggle ────────────────────────────────────────────────────────
 
 func _on_login_button_pressed() -> void:
@@ -184,12 +197,12 @@ func _update_auth_mode_ui() -> void:
 		_auth_mode_label.text = "Register"
 		_auth_button.text = "Register"
 		_email_edit.visible = true
-		_over_18_check.visible = true
+		_dob_edit.visible = true
 	else:
 		_auth_mode_label.text = "Login"
 		_auth_button.text = "Login"
 		_email_edit.visible = false
-		_over_18_check.visible = false
+		_dob_edit.visible = false
 
 
 # ─── Auth submission ──────────────────────────────────────────────────────────
@@ -216,8 +229,9 @@ func _on_auth_button_pressed() -> void:
 		if email == "":
 			_show_status("Email is required.")
 			return
-		if not _over_18_check.button_pressed:
-			_show_status("You must confirm you are 18 or older to register.")
+		var dob := _dob_edit.text.strip_edges()
+		if not _is_valid_dob(dob):
+			_show_status("Enter your date of birth as YYYY-MM-DD.")
 			return
 
 		_auth_button.disabled = true
@@ -225,7 +239,7 @@ func _on_auth_button_pressed() -> void:
 		_is_authenticating = true
 		_clear_status()
 
-		var result := await ApiClient.register(username, email, password, true)
+		var result := await ApiClient.register(username, email, password, dob)
 		await _on_auth_complete(result)
 	else:
 		_auth_button.disabled = true
@@ -251,7 +265,7 @@ func _on_auth_complete(result: Dictionary) -> void:
 		_username_edit.visible = false
 		_password_edit.visible = false
 		_email_edit.visible = false
-		_over_18_check.visible = false
+		_dob_edit.visible = false
 		_auth_button.visible = false
 		_auth_mode_label.visible = false
 		_status_label.visible = false
diff --git a/scripts/mp_game_flow_client.gd b/scripts/mp_game_flow_client.gd
index 68d716f..36fe0ff 100644
--- a/scripts/mp_game_flow_client.gd
+++ b/scripts/mp_game_flow_client.gd
@@ -30,7 +30,7 @@ func _run() -> void:
 	var session := root.get_node("Session")
 
 	var uname := "mpflow_%s_%d" % [role, int(Time.get_unix_time_from_system() * 1000) % 1000000]
-	var reg: Dictionary = await api.register(uname, uname + "@e.com", "secret123", true)
+	var reg: Dictionary = await api.register(uname, uname + "@e.com", "secret123", "1990-01-01")
 	if not reg.ok:
 		print("RESULT %s register_failed %s" % [role, reg.detail])
 		quit(1); return
diff --git a/scripts/smoke_test_auth.gd b/scripts/smoke_test_auth.gd
index cc9182f..cfdde54 100644
--- a/scripts/smoke_test_auth.gd
+++ b/scripts/smoke_test_auth.gd
@@ -10,7 +10,7 @@ extends SceneTree
 ## Tests:
 ##   1. Register a unique user → 201 + token stored.
 ##   2. Register the same user again → 409 "Username already registered".
-##   3. Register with over_18=false → 400 "Must be 18 or older".
+##   3. Register with an under-18 DOB → 403 "at least 18".
 ##   4. Login with correct credentials → 200 + token stored.
 ##   5. Login with wrong password → 401 "Incorrect username or password".
 ##   6. Login with non-existent user → 401 "Incorrect username or password".
@@ -44,7 +44,7 @@ func _run() -> void:
 	var email := "smoke_%d@test.example.com" % unique_id
 
 	print("\n=== Test 1: Register unique user ===")
-	var result := await api.register(username, email, TEST_PASSWORD, true)
+	var result := await api.register(username, email, TEST_PASSWORD, "1990-01-01")
 	if _check("register returns ok", result.ok) \
 			and _check("register status is 201", result.status == 201) \
 			and _check("register stores token", api.has_token()):
@@ -55,7 +55,7 @@ func _run() -> void:
 
 	# --- Test 2: Register same user again (duplicate) ---
 	print("\n=== Test 2: Duplicate username ===")
-	result = await api.register(username, email, TEST_PASSWORD, true)
+	result = await api.register(username, email, TEST_PASSWORD, "1990-01-01")
 	if _check("duplicate register not ok", not result.ok) \
 			and _check("duplicate status is 409", result.status == 409) \
 			and _check("duplicate detail mentions username",
@@ -65,14 +65,16 @@ func _run() -> void:
 		failed += 1
 		print("  detail: ", result.detail)
 
-	# --- Test 3: Register with over_18=false ---
-	print("\n=== Test 3: over_18=false registration ===")
+	# --- Test 3: Register with an under-18 date of birth ---
+	print("\n=== Test 3: under-18 registration ===")
 	var child_username := "child_%d" % unique_id
 	var child_email := "child_%d@test.example.com" % unique_id
-	result = await api.register(child_username, child_email, TEST_PASSWORD, false)
-	if _check("over_18=false register not ok", not result.ok) \
-			and _check("over_18=false status is 400", result.status == 400) \
-			and _check("over_18=false detail mentions age",
+	var now := Time.get_datetime_dict_from_system()
+	var minor_dob := "%04d-01-01" % (int(now["year"]) - 14)
+	result = await api.register(child_username, child_email, TEST_PASSWORD, minor_dob)
+	if _check("under-18 register not ok", not result.ok) \
+			and _check("under-18 status is 403", result.status == 403) \
+			and _check("under-18 detail mentions age",
 					"18" in result.detail):
 		passed += 1
 	else:
diff --git a/scripts/smoke_test_e2e.gd b/scripts/smoke_test_e2e.gd
index 692aec9..e61fc78 100644
--- a/scripts/smoke_test_e2e.gd
+++ b/scripts/smoke_test_e2e.gd
@@ -69,7 +69,7 @@ func _run() -> void:
 
 	# --- Step 2: Register -----------------------------------------------------
 	print("\n=== Step 2: Register (POST /api/auth/register) ===")
-	var reg: Dictionary = await api.register(username, email, TEST_PASSWORD, true)
+	var reg: Dictionary = await api.register(username, email, TEST_PASSWORD, "1990-01-01")
 	var reg_token := _extract_token(reg)
 	var reg_ok: bool = (
 		reg.ok
diff --git a/scripts/smoke_test_enter_world.gd b/scripts/smoke_test_enter_world.gd
index d0377d8..7ab0ca6 100644
--- a/scripts/smoke_test_enter_world.gd
+++ b/scripts/smoke_test_enter_world.gd
@@ -35,7 +35,7 @@ func _run() -> void:
 	var unique_id: int = int(Time.get_unix_time_from_system() * 1000) + randi() % 100000
 	var username := "enterworld_%d" % unique_id
 	var email := "enterworld_%d@test.example.com" % unique_id
-	var reg_result: Dictionary = await api.register(username, email, "SmokeTest123!", true)
+	var reg_result: Dictionary = await api.register(username, email, "SmokeTest123!", "1990-01-01")
 	if not _check("setup: register succeeded", reg_result.ok):
 		print("  detail: ", reg_result.detail)
 		_finish()
diff --git a/scripts/smoke_test_main_menu_back.gd b/scripts/smoke_test_main_menu_back.gd
index 6313c8d..99aa42b 100644
--- a/scripts/smoke_test_main_menu_back.gd
+++ b/scripts/smoke_test_main_menu_back.gd
@@ -49,7 +49,7 @@ func _run() -> void:
 	var username := USERNAME % unique_id
 	var email := EMAIL % unique_id
 	print("\n=== Setup: register ", username, " ===")
-	var register_result: Dictionary = await api.register(username, email, PASSWORD, true)
+	var register_result: Dictionary = await api.register(username, email, PASSWORD, "1990-01-01")
 	if not _check("register succeeds", register_result.ok):
 		print("  detail: ", register_result.detail)
 		_finish()
diff --git a/scripts/smoke_test_main_menu_full_flow.gd b/scripts/smoke_test_main_menu_full_flow.gd
index 71cc34d..9a23105 100644
--- a/scripts/smoke_test_main_menu_full_flow.gd
+++ b/scripts/smoke_test_main_menu_full_flow.gd
@@ -25,7 +25,7 @@ func _run() -> void:
 	var username_edit: LineEdit = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/UsernameEdit")
 	var password_edit: LineEdit = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/PasswordEdit")
 	var email_edit: LineEdit = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/EmailEdit")
-	var over_18_check: CheckBox = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/Over18Check")
+	var dob_edit: LineEdit = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/DobEdit")
 	var auth_button: Button = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/AuthButton")
 	var auth_mode_label: Label = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/AuthModeLabel")
 	var welcome_label: Label = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/WelcomeLabel")
@@ -46,7 +46,7 @@ func _run() -> void:
 	username_edit.text = "mainmenu_e2e_%d" % unique_id
 	password_edit.text = "TestPass123!"
 	email_edit.text = "mainmenu_e2e_%d@test.example.com" % unique_id
-	over_18_check.button_pressed = true
+	dob_edit.text = "1990-01-01"
 
 	# Call the submit handler directly (awaited) rather than via
 	# auth_button.pressed.emit() -- a synthetic .emit() in --script/
@@ -68,7 +68,7 @@ func _run() -> void:
 	_check("Username edit hidden after auth", not username_edit.visible)
 	_check("Password edit hidden after auth", not password_edit.visible)
 	_check("Email edit hidden after auth", not email_edit.visible)
-	_check("Over18 checkbox hidden after auth", not over_18_check.visible)
+	_check("DOB field hidden after auth", not dob_edit.visible)
 	_check("Auth button hidden after auth", not auth_button.visible)
 	_check("Auth mode label hidden after auth", not auth_mode_label.visible)
 	_check("Welcome label contains username", welcome_label.text.begins_with("Welcome, mainmenu_e2e_"))
diff --git a/scripts/smoke_test_main_menu_ui.gd b/scripts/smoke_test_main_menu_ui.gd
index f5d62ab..248ceb0 100644
--- a/scripts/smoke_test_main_menu_ui.gd
+++ b/scripts/smoke_test_main_menu_ui.gd
@@ -31,7 +31,7 @@ func _run() -> void:
 	var auth_panel: PanelContainer = instance.get_node("CenterContainer/VBoxContainer/AuthPanel")
 	var auth_mode_label: Label = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/AuthModeLabel")
 	var email_edit: LineEdit = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/EmailEdit")
-	var over_18_check: CheckBox = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/Over18Check")
+	var dob_edit: LineEdit = instance.get_node("CenterContainer/VBoxContainer/AuthPanel/MarginContainer/AuthVBox/DobEdit")
 
 	# --- Test 1: auth panel starts hidden ---
 	if _check("auth panel starts hidden", not auth_panel.visible):
@@ -58,7 +58,7 @@ func _run() -> void:
 	else:
 		failed += 1
 
-	if _check("Over18 checkbox hidden in Login mode", not over_18_check.visible):
+	if _check("DOB field hidden in Login mode", not dob_edit.visible):
 		passed += 1
 	else:
 		failed += 1
@@ -82,7 +82,7 @@ func _run() -> void:
 	else:
 		failed += 1
 
-	if _check("Over18 checkbox visible in Register mode", over_18_check.visible):
+	if _check("DOB field visible in Register mode", dob_edit.visible):
 		passed += 1
 	else:
 		failed += 1
@@ -101,7 +101,7 @@ func _run() -> void:
 	else:
 		failed += 1
 
-	if _check("Over18 checkbox hidden after switching back to Login", not over_18_check.visible):
+	if _check("DOB field hidden after switching back to Login", not dob_edit.visible):
 		passed += 1
 	else:
 		failed += 1
diff --git a/scripts/smoke_test_world_list.gd b/scripts/smoke_test_world_list.gd
index b0b6231..1414ebb 100644
--- a/scripts/smoke_test_world_list.gd
+++ b/scripts/smoke_test_world_list.gd
@@ -58,7 +58,7 @@ func _run() -> void:
 	var unique_id: int = int(Time.get_unix_time_from_system() * 1000) + randi() % 100000
 	var username := "worldlist_smoke_%d" % unique_id
 	var email := "worldlist_smoke_%d@test.example.com" % unique_id
-	var reg_result: Dictionary = await api.register(username, email, "SmokeTest123!", true)
+	var reg_result: Dictionary = await api.register(username, email, "SmokeTest123!", "1990-01-01")
 	if not _check("setup: register succeeded", reg_result.ok):
 		print("  detail: ", reg_result.detail)
 		quit(1)