diff --git a/src/ytstudio/commands/analytics.py b/src/ytstudio/commands/analytics.py
index 6db7962..0aea481 100644
--- a/src/ytstudio/commands/analytics.py
+++ b/src/ytstudio/commands/analytics.py
@@ -2,7 +2,7 @@
 import io
 import json
 from dataclasses import asdict, dataclass
-from datetime import datetime, timedelta
+from datetime import date, datetime, timedelta
 
 import typer
 
@@ -318,6 +318,35 @@ def _parse_comma_list(value: str) -> list[str]:
     return [v.strip() for v in value.split(",") if v.strip()]
 
 
+def _align_date_range(
+    dimension_names: list[str], start_date: str, end_date: str
+) -> tuple[str, str]:
+    """Snap dates to the boundaries the YouTube Analytics API requires.
+
+    month: both ends must be the first of a month. The API rejects other days,
+    it does not snap. So snap both ends DOWN to the first of their month.
+    week: API weeks begin on Sunday. Snap both ends back to their Sunday.
+    See https://developers.google.com/youtube/analytics/dimensions (time periods).
+    Other dimensions (day, country, ...) are returned unchanged.
+    """
+    if DimensionName.MONTH in dimension_names:
+        return _snap_to_month_start(start_date), _snap_to_month_start(end_date)
+    if "week" in dimension_names:
+        return _snap_to_week_start(start_date), _snap_to_week_start(end_date)
+    return start_date, end_date
+
+
+def _snap_to_month_start(value: str) -> str:
+    d = date.fromisoformat(value)
+    return d.replace(day=1).isoformat()
+
+
+def _snap_to_week_start(value: str) -> str:
+    # weekday(): Mon=0 .. Sun=6; days back to the preceding Sunday.
+    d = date.fromisoformat(value)
+    return (d - timedelta(days=(d.weekday() + 1) % 7)).isoformat()
+
+
 def _format_query_response(response: dict, output: str) -> None:
     headers = [h["name"] for h in response.get("columnHeaders", [])]
     rows = response.get("rows", [])
@@ -449,9 +478,10 @@ def query(
                 raise typer.Exit(1)
         filters_str = ";".join(filter_list)
 
-    # Build dates
+    # Build dates, then snap to dimension-required boundaries (month, week).
     end_date = end or datetime.now().strftime("%Y-%m-%d")
     start_date = start or (datetime.now() - timedelta(days=days)).strftime("%Y-%m-%d")
+    start_date, end_date = _align_date_range(dimension_names, start_date, end_date)
 
     # The video dimension requires sort + maxResults per YouTube API docs
     if DimensionName.VIDEO in dimension_names and (not sort or not limit):
diff --git a/tests/test_analytics.py b/tests/test_analytics.py
index d84fbfd..c0700e6 100644
--- a/tests/test_analytics.py
+++ b/tests/test_analytics.py
@@ -4,6 +4,7 @@
 import typer
 from typer.testing import CliRunner
 
+from ytstudio.commands.analytics import _align_date_range
 from ytstudio.main import app
 from ytstudio.ui import format_number, set_raw_output
 
@@ -392,3 +393,62 @@ def test_json_output(self):
         data = json.loads(result.output)
         assert isinstance(data, list)
         assert any(d["name"] == "country" for d in data)
+
+
+class TestAlignDateRange:
+    def test_month_snaps_start_down(self):
+        assert _align_date_range(["month"], "2026-04-17", "2026-06-01") == (
+            "2026-04-01",
+            "2026-06-01",
+        )
+
+    def test_month_snaps_end_down(self):
+        assert _align_date_range(["month"], "2026-04-01", "2026-06-23") == (
+            "2026-04-01",
+            "2026-06-01",
+        )
+
+    def test_month_days_derived_non_aligned(self):
+        # --days 365 from a mid-month "today" yields two arbitrary days.
+        assert _align_date_range(["month"], "2025-06-18", "2026-06-18") == (
+            "2025-06-01",
+            "2026-06-01",
+        )
+
+    def test_month_already_aligned_unchanged(self):
+        assert _align_date_range(["month"], "2026-04-01", "2026-06-01") == (
+            "2026-04-01",
+            "2026-06-01",
+        )
+
+    def test_month_same_month_range(self):
+        assert _align_date_range(["month"], "2026-04-10", "2026-04-25") == (
+            "2026-04-01",
+            "2026-04-01",
+        )
+
+    def test_day_untouched(self):
+        assert _align_date_range(["day"], "2026-04-17", "2026-06-23") == (
+            "2026-04-17",
+            "2026-06-23",
+        )
+
+    def test_no_dimension_untouched(self):
+        assert _align_date_range([], "2026-04-17", "2026-06-23") == (
+            "2026-04-17",
+            "2026-06-23",
+        )
+
+    def test_week_snaps_back_to_sunday(self):
+        # 2026-06-18 is a Thursday; preceding Sunday is 2026-06-14.
+        assert _align_date_range(["week"], "2026-06-18", "2026-06-18") == (
+            "2026-06-14",
+            "2026-06-14",
+        )
+
+    def test_week_sunday_unchanged(self):
+        # 2026-06-14 is a Sunday; stays put.
+        assert _align_date_range(["week"], "2026-06-14", "2026-06-21") == (
+            "2026-06-14",
+            "2026-06-21",
+        )