diff --git a/python_carbon/__init__.py b/python_carbon/__init__.py
index 19d608e..c610f93 100644
--- a/python_carbon/__init__.py
+++ b/python_carbon/__init__.py
@@ -561,8 +561,10 @@ def endOfDay(self) -> 'Carbon':
         )
 
     def startOfWeek(self) -> 'Carbon':
+        start_of_week = self._date - timedelta(days=self._date.weekday())
+
         return Carbon(
-            (self._date - timedelta(days=self._date.weekday())).replace(
+            start_of_week.replace(
                 hour=0,
                 minute=0,
                 second=0,
@@ -571,8 +573,10 @@ def startOfWeek(self) -> 'Carbon':
         )
 
     def endOfWeek(self) -> 'Carbon':
+        end_of_week = self.startOfWeek().toDatetime() + timedelta(days=6)
+
         return Carbon(
-            self.startOfWeek().addDays(6).toDatetime().replace(
+            end_of_week.replace(
                 hour=23,
                 minute=59,
                 second=59,
@@ -604,7 +608,7 @@ def endOfMonth(self) -> 'Carbon':
 
     def startOfYear(self) -> 'Carbon':
         return Carbon(
-            self.startOfWeek().addDays(6).toDatetime().replace(
+            self._date.replace(
                 month=1,
                 day=1,
                 hour=0,
@@ -616,7 +620,7 @@ def startOfYear(self) -> 'Carbon':
 
     def endOfYear(self) -> 'Carbon':
         return Carbon(
-            self.startOfWeek().addDays(6).toDatetime().replace(
+            self._date.replace(
                 month=12,
                 day=31,
                 hour=23,
diff --git a/tests/test_python_carbon.py b/tests/test_python_carbon.py
index 324f793..fadac7a 100644
--- a/tests/test_python_carbon.py
+++ b/tests/test_python_carbon.py
@@ -63,6 +63,18 @@ def test_start_and_end_methods(self) -> None:
         self.assertEqual(end_of_hour.second, 59)
         self.assertEqual(end_of_hour.microsecond, 999999)
 
+    def test_start_end_week_and_year_exact_values(self) -> None:
+        dt = Carbon.parse('2021-08-18 14:15:16.123456')
+
+        self.assertEqual(dt.startOfWeek().toDateTimeString(with_milliseconds=True), '2021-08-16 00:00:00.000000')
+        self.assertEqual(dt.endOfWeek().toDateTimeString(with_milliseconds=True), '2021-08-22 23:59:59.999999')
+        self.assertEqual(dt.startOfYear().toDateTimeString(with_milliseconds=True), '2021-01-01 00:00:00.000000')
+        self.assertEqual(dt.endOfYear().toDateTimeString(with_milliseconds=True), '2021-12-31 23:59:59.999999')
+
+        sunday = Carbon.parse('2021-08-22 10:00:00')
+        self.assertEqual(sunday.startOfWeek().toDateTimeString(), '2021-08-16 00:00:00')
+        self.assertEqual(sunday.endOfWeek().toDateTimeString(), '2021-08-22 23:59:59')
+
     def test_add_sub_and_last_day_of_month(self) -> None:
         self.assertTrue(Carbon.parse('2021-08-31').isLastDayOfMonth())