Merge pull request #871 from rrott/fix/870-may-1st-missing

Fixed issue with rendering calendar incorrectly when first day of a m…

components/date_picker/CalendarDay.js

@@ -20,8 +20,9 @@ class Day extends Component {
   dayStyle () {
     if (this.props.day === 1) {
       const e = (this.props.sundayFirstDayOfWeek) ? 0 : 1;
+      const firstDay = time.getFirstWeekDay(this.props.viewDate) - e;
       return {
-        marginLeft: `${(time.getFirstWeekDay(this.props.viewDate) - e) * 100 / 7}%`
+        marginLeft: `${ (firstDay >= 0 ? firstDay : 6) * 100 / 7 }%`
       };
     }
   }