fix

Samples/UIWidgetsSamples_2019_4/Packages/manifest.json

     "com.unity.collab-proxy": "1.2.16",
     "com.unity.ide.rider": "1.1.4",
     "com.unity.ide.vscode": "1.2.1",
-    "com.unity.uiwidgets": "file:../../../com.unity.uiwidgets",
-    "com.unity.test-framework": "1.1.14",
+    "com.unity.test-framework": "1.1.16",
+    "com.unity.uiwidgets": "file:../../../com.unity.uiwidgets",
     "com.unity.modules.ai": "1.0.0",
     "com.unity.modules.androidjni": "1.0.0",
     "com.unity.modules.animation": "1.0.0",

Samples/UIWidgetsSamples_2019_4/ProjectSettings/ProjectVersion.txt

-m_EditorVersion: 2019.4.2f1
-m_EditorVersionWithRevision: 2019.4.2f1 (f997fc5c673b)
+m_EditorVersion: 2019.4.10f1
+m_EditorVersionWithRevision: 2019.4.10f1 (a819905b7a01)

com.unity.uiwidgets/Runtime/cupertino/date_picker.cs

         }
         DateTime  selectedDateTime {
             get {
-                return new DateTime(
+                return (new DateTime(
-                    initialDateTime.Day + selectedDayFromInitial,
+                    initialDateTime.Day,
-                );
+                )).AddDays(selectedDayFromInitial);
             }
         }
         void _onSelectedItemChange(int index) {
             );
         }
         bool _isValidHour(int meridiemIndex, int hourIndex) {
-            DateTime rangeStart = new DateTime(
+            DateTime rangeStart = (new DateTime(
-                initialDateTime.Day + selectedDayFromInitial,
+                initialDateTime.Day,
-            );
+            )).AddDays(selectedDayFromInitial);
 
             // The end value of the range is exclusive, i.e. [rangeStart, rangeEnd).
             DateTime rangeEnd = rangeStart.Add(new TimeSpan(0,1,0,0));
             for (int index = 0; index < 24; index++) {
                 int minute = index * widget.minuteInterval;
 
-                DateTime date = new DateTime(
+                DateTime date = (new DateTime(
-                    initialDateTime.Day + selectedDayFromInitial,
+                    initialDateTime.Day,
-                );
+                )).AddDays(selectedDayFromInitial);
 
                 bool isInvalidMinute = (widget.minimumDate?.CompareTo(date) < 0 )
                                        || (widget.maximumDate?.CompareTo(date) > 0);

com.unity.uiwidgets/Runtime/gestures/events.cs

             properties.add(new IntProperty("buttons", buttons, defaultValue: 0, level: DiagnosticLevel.debug));
             properties.add(new DiagnosticsProperty<bool>("down", down, level: DiagnosticLevel.debug));
             properties.add(
-                new FloatProperty("pressure", pressure, defaultValue: 1.0, level: DiagnosticLevel.debug));
-            properties.add(new FloatProperty("pressureMin", pressureMin, defaultValue: 1.0,
+                new FloatProperty("pressure", pressure, defaultValue: 1.0f, level: DiagnosticLevel.debug));
+            properties.add(new FloatProperty("pressureMin", pressureMin, defaultValue: 1.0f,
-            properties.add(new FloatProperty("pressureMax", pressureMax, defaultValue: 1.0,
+            properties.add(new FloatProperty("pressureMax", pressureMax, defaultValue: 1.0f,
-                new FloatProperty("distance", distance, defaultValue: 0.0, level: DiagnosticLevel.debug));
-            properties.add(new FloatProperty("distanceMin", distanceMin, defaultValue: 0.0,
+                new FloatProperty("distance", distance, defaultValue: 0.0f, level: DiagnosticLevel.debug));
+            properties.add(new FloatProperty("distanceMin", distanceMin, defaultValue: 0.0f,
-            properties.add(new FloatProperty("distanceMax", distanceMax, defaultValue: 0.0,
+            properties.add(new FloatProperty("distanceMax", distanceMax, defaultValue: 0.0f,
-            properties.add(new FloatProperty("size", size, defaultValue: 0.0, level: DiagnosticLevel.debug));
-            properties.add(new FloatProperty("radiusMajor", radiusMajor, defaultValue: 0.0,
+            properties.add(new FloatProperty("size", size, defaultValue: 0.0f, level: DiagnosticLevel.debug));
+            properties.add(new FloatProperty("radiusMajor", radiusMajor, defaultValue: 0.0f,
-            properties.add(new FloatProperty("radiusMinor", radiusMinor, defaultValue: 0.0,
+            properties.add(new FloatProperty("radiusMinor", radiusMinor, defaultValue: 0.0f,
-            properties.add(new FloatProperty("radiusMin", radiusMin, defaultValue: 0.0,
+            properties.add(new FloatProperty("radiusMin", radiusMin, defaultValue: 0.0f,
-            properties.add(new FloatProperty("radiusMax", radiusMax, defaultValue: 0.0,
+            properties.add(new FloatProperty("radiusMax", radiusMax, defaultValue: 0.0f,
-            properties.add(new FloatProperty("orientation", orientation, defaultValue: 0.0,
+            properties.add(new FloatProperty("orientation", orientation, defaultValue: 0.0f,
-            properties.add(new FloatProperty("tilt", tilt, defaultValue: 0.0, level: DiagnosticLevel.debug));
+            properties.add(new FloatProperty("tilt", tilt, defaultValue: 0.0f, level: DiagnosticLevel.debug));
             properties.add(new IntProperty("platformData", platformData, defaultValue: 0,
                 level: DiagnosticLevel.debug));
             properties.add(new FlagProperty("obscured", value: obscured, ifTrue: "obscured",