diff --git a/.dart_tool/pub/bin/sdk-version b/.dart_tool/pub/bin/sdk-version
index c380242..07203f2 100644
--- a/.dart_tool/pub/bin/sdk-version
+++ b/.dart_tool/pub/bin/sdk-version
@@ -1 +1 @@
-2.0.0-dev.32.0
+2.1.0-dev.1.0.flutter-ccb16f7282
diff --git a/.dart_tool/pub/bin/test/test.dart.snapshot b/.dart_tool/pub/bin/test/test.dart.snapshot
deleted file mode 100644
index 6b07ff3..0000000
Binary files a/.dart_tool/pub/bin/test/test.dart.snapshot and /dev/null differ
diff --git a/.dart_tool/pub/bin/test/test.dart.snapshot.dart2 b/.dart_tool/pub/bin/test/test.dart.snapshot.dart2
new file mode 100644
index 0000000..5d6784b
Binary files /dev/null and b/.dart_tool/pub/bin/test/test.dart.snapshot.dart2 differ
diff --git a/lib/date_utils.dart b/lib/date_utils.dart
index bd4ab35..dd067aa 100644
--- a/lib/date_utils.dart
+++ b/lib/date_utils.dart
@@ -15,6 +15,8 @@ class Utils {
   static String fullDayFormat(DateTime d) => _fullDayFormat.format(d);
   static String apiDayFormat(DateTime d) => _apiDayFormat.format(d);
 
+  static bool _isMondayFirstDayOfWeek = false;
+
   static const List<String> weekdays = const [
     "Sun",
     "Mon",
@@ -49,11 +51,19 @@ class Utils {
     return new DateTime(month.year, month.month);
   }
 
+  static void setIsMondayFirstDayOfWeek(bool isMonday) {
+    _isMondayFirstDayOfWeek = isMonday;
+  }
+
   static DateTime firstDayOfWeek(DateTime day) {
     /// Handle Daylight Savings by setting hour to 12:00 Noon
     /// rather than the default of Midnight
     day = new DateTime.utc(day.year, day.month, day.day, 12);
 
+    if (_isMondayFirstDayOfWeek) {
+      return day.subtract(new Duration(days: day.weekday - 1));
+    }
+
     /// Weekday is on a 1-7 scale Monday - Sunday,
     /// This Calendar works from Sunday - Monday
     var decreaseNum = day.weekday % 7;
@@ -65,6 +75,10 @@ class Utils {
     /// rather than the default of Midnight
     day = new DateTime.utc(day.year, day.month, day.day, 12);
 
+    if (_isMondayFirstDayOfWeek) {
+      return day.add(new Duration(days: day.weekday - 1));
+    }
+
     /// Weekday is on a 1-7 scale Monday - Sunday,
     /// This Calendar's Week starts on Sunday
     var increaseNum = day.weekday % 7;
diff --git a/pubspec.yaml b/pubspec.yaml
index e0b99fe..67bfbad 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -13,4 +13,4 @@ dependencies:
   intl: ^0.15.0
 
 dev_dependencies:
-  test: ^0.12.0
+  test: ^1.3.0
diff --git a/test/date_utils_test.dart b/test/date_utils_test.dart
index 375329c..8a85e08 100644
--- a/test/date_utils_test.dart
+++ b/test/date_utils_test.dart
@@ -97,12 +97,21 @@ void main() {
         var lastDayOfCurrentWeek = Utils.lastDayOfWeek(today);
 
         expect(
-            Utils
-                .daysInRange(firstDayOfCurrentWeek, lastDayOfCurrentWeek)
+            Utils.daysInRange(firstDayOfCurrentWeek, lastDayOfCurrentWeek)
                 .toList()
                 .length,
             7);
       });
     }
+    test('setWhichIsFirstDayOfWeek', () {
+      var date = new DateTime(2018, 9, 6);
+      Utils.setIsMondayFirstDayOfWeek(true);
+
+      var firstDayOfWeek = new DateTime(2018, 9, 3);
+      var lastDayOfWeek = new DateTime(2018, 9, 9);
+
+      expect(Utils.firstDayOfWeek(date).day, firstDayOfWeek.day);
+      expect(Utils.lastDayOfWeek(date).day, lastDayOfWeek.day);
+    });
   });
 }