Add circle to day view

components/header.js

 import React, { Component } from 'react'
 import {
   View,
-  Text
+  Text,
+  Dimensions
 } from 'react-native'
 import styles, { iconStyles } from '../styles'
 import Icon from 'react-native-vector-icons/MaterialCommunityIcons'
@@ -9,9 +10,11 @@ import { formatDateForViewHeader } from '../components/cycle-day/labels/format'
 
 export default class Header extends Component {
   render() {
+    const middle = Dimensions.get('window').width / 2
     return (
       this.props.isCycleDayOverView ?
         <View style={[styles.header, styles.headerCycleDay]}>
+          <View style={styles.accentCircle} left={middle - styles.accentCircle.width / 2}/>
           <Icon
             name='arrow-left-drop-circle'
             {...iconStyles.navigationArrow}