diff --git a/redmine_reporter/config.py b/redmine_reporter/config.py
index 11a4e62..7a5bd6f 100644
--- a/redmine_reporter/config.py
+++ b/redmine_reporter/config.py
@@ -370,8 +370,10 @@ class Config:
     def get_default_date_range(cls) -> str:
         from_env = os.getenv("DEFAULT_FROM_DATE", "").strip()
         to_env = os.getenv("DEFAULT_TO_DATE", "").strip()
-        if from_env and to_env:
-            return f"{from_env}--{to_env}"
+        today_str = date.today().isoformat()
+
+        if from_env:
+            return f"{from_env}--{to_env or today_str}"
 
         if (
             cls._app
@@ -386,17 +388,12 @@ class Config:
             )
             return f"{nf}--{nt}"
 
-        if cls._app and cls._app.period_default_from and cls._app.period_default_to:
-            return f"{cls._app.period_default_from}--{cls._app.period_default_to}"
+        if cls._app and cls._app.period_default_from:
+            default_to = cls._app.period_default_to or today_str
+            return f"{cls._app.period_default_from}--{default_to}"
 
-        today = date.today()
-        start = today.replace(day=1)
-        if today.month == 12:
-            next_month = today.replace(year=today.year + 1, month=1, day=1)
-        else:
-            next_month = today.replace(month=today.month + 1, day=1)
-        end = next_month - timedelta(days=1)
-        return f"{start.isoformat()}--{end.isoformat()}"
+        start = date.today().replace(day=1)
+        return f"{start.isoformat()}--{today_str}"
 
     @classmethod
     def validate(cls) -> None:
diff --git a/tests/test_config.py b/tests/test_config.py
index 21348d5..c1feb7b 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -79,21 +79,29 @@ def test_get_default_date_range_from_env():
     assert Config.get_default_date_range() == "2026-01-01--2026-01-31"
 
 
+@mock.patch.dict(
+    os.environ,
+    {"DEFAULT_FROM_DATE": "2026-01-01"},
+    clear=True,
+)
+def test_get_default_date_range_from_env_without_to():
+    """Если DEFAULT_TO_DATE не задан, конец периода — сегодня."""
+    from datetime import date
+
+    today = date.today().isoformat()
+    assert Config.get_default_date_range() == f"2026-01-01--{today}"
+
+
 @mock.patch.dict(os.environ, {}, clear=True)
 def test_get_default_date_range_fallback():
-    """Если даты не заданы -- используется текущий месяц."""
-    from datetime import date, timedelta
+    """Если даты не заданы -- используется текущий месяц с начала до сегодня."""
+    from datetime import date
 
     today = date.today()
     start = today.replace(day=1)
-    if today.month == 12:
-        next_month = today.replace(year=today.year + 1, month=1, day=1)
-    else:
-        next_month = today.replace(month=today.month + 1, day=1)
-    end = next_month - timedelta(days=1)
 
     result = Config.get_default_date_range()
-    assert result == f"{start.isoformat()}--{end.isoformat()}"
+    assert result == f"{start.isoformat()}--{today.isoformat()}"
 
 
 @mock.patch.dict(os.environ, {}, clear=True)
@@ -567,6 +575,24 @@ class TestDefaultDateRangeWithLastUsed:
             result = Config.get_default_date_range()
             assert result == "2026-04-01--2026-04-15"
 
+    @mock.patch.dict(os.environ, {}, clear=True)
+    def test_falls_back_to_today_when_default_to_missing(self):
+        """Если default_from задан, а default_to нет — конец периода сегодня."""
+        from datetime import date
+
+        with tempfile.TemporaryDirectory() as tmp:
+            yaml_path = Path(tmp) / "config.yml"
+            yaml_path.write_text(
+                "period:\n"
+                "  precision: date\n"
+                "  dynamic: false\n"
+                "  default_from: '2026-04-01'\n"
+            )
+            Config._app = AppConfig.from_yaml(yaml_path)
+            today = date.today().isoformat()
+            result = Config.get_default_date_range()
+            assert result == f"2026-04-01--{today}"
+
 
 class TestGetEmailConfig:
     """Tests for Config.get_email_config()."""