How do you group a list of transactions by the date they're created in react native?

import React from 'react';
import {
  Text,
  SafeAreaView,
  StatusBar,
  ActivityIndicator,
  FlatList,
  View,
  List,
  Image,
  SectionList,
} from 'react-native';
import moment from 'moment';
import transactions from '../testdata/transactions.json';
import Icon from 'react-native-ionicons'

var datetest = [moment(transactions[0].addedtime).calendar()];
 
moment.locale('en-uk', {
  calendar: {
    lastDay: '[Yesterday ]',
    sameDay: '[Today]',
    nextDay: '[Tomorrow]',
    lastWeek: 'L',
    nextWeek: 'dddd',
    sameElse: 'L',
  },
});

class TransactionsComponent extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      isLoading: true,
      dataSource: [],
      epochDate: [],
    };
  }

  componentDidMount() {
    this.setState({
      isLoading: false,
      dataSource: transactions,
      epochDate: datetest,
    });
  }

  
  renderSeparator = () => {
    return (<View
        style={{
          height: 0,
          width: '100%',
          backgroundColor: '#F5F5F5	',
          marginLeft: '0%',
        }}
      />
    );
  };

  render() {
    if (this.state.isLoading) {
      return (
        <View style={{flex: 1, padding: 20}}><ActivityIndicator /></View>
      );
    }
  }


 

  render() {
    return (
      <View style={{width: '100%'}}><FlatList
          data={this.state.dataSource}
          renderItem={({item}) => (<View
              style={{
                flex: 1,
                flexDirection: 'column',
                borderBottomColor: '#5AA8C8',
                borderBottomWidth: 1,
                paddingBottom: 10,
              }}>

              
              { <View style={{marginLeft: '3%'}}><Text style={{fontWeight: 'bold', fontSize: 18}}>
                  {moment(item.addedtime).calendar()}</Text></View> }<View style={{marginLeft: '5%', flexDirection: 'row', flex: 2,}}><View
                  style={{flexDirection: 'row', alignItems: 'center', flex: 3}}><Image
                    style={{width: 40, height: 40}}
                    source={{uri: item.iconblob}}
                  /><Text
                    style={{fontSize: 16, color: 'grey', fontWeight: 'bold'}}>
                    {''}
                    {item.merchantname}</Text></View><View
                  style={{
                    flex: 1,
                    flexDirection: 'row',
                    alignItems: 'center',
                    justifyContent: 'flex-end',
                    marginRight: '3%',
                  }}><Text style={{fontSize: 18, color: 'black'}}><Text style={{fontSize: 12, color: 'grey'}}>CHF</Text>
                    {parseFloat(item.billingamountauthorised / 100).toFixed(2)}</Text><View style= {{flex :6, flexDirection:"row", justifyContent:"flex-end"}}><Icon name="arrow-dropright" color="#5AA8C8" /></View></View></View></View>
          )}
          keyExtractor={item => item.uniqueref}
          //containerStyle={{borderBottomWidth: 0}}
        /></View>
    );
  }
}

export default TransactionsComponent;

[   
    {"billingamountauthorised": "1","iconblob": "https://is1-ssl.mzstatic.com/image/thumb/Purple114/v4/cb/cf/bb/cbcfbb61-4d03-4f4e-ecf7-b7582688435f/source/512x512bb.jpg","merchantname": "K Kiosk Sihlquai","merchantstreet": "Sihlquai","addedtime": 1576590342000,"uniqueref": "A446806878486B5B"
},
{"billingamountauthorised": "750","iconblob": "https://upload.wikimedia.org/wikipedia/en/thumb/d/d3/Starbucks_Corporation_Logo_2011.svg/1024px-Starbucks_Corporation_Logo_2011.svg.png","merchantname": "Starbucks","merchantstreet": "Rue du Mont-Blanc","addedtime": 1576590342000,"uniqueref": "D0868EB65DC2DE585"
},
    {"billingamountauthorised": "1","iconblob": "https://is1-ssl.mzstatic.com/image/thumb/Purple114/v4/cb/cf/bb/cbcfbb61-4d03-4f4e-ecf7-b7582688435f/source/512x512bb.jpg","merchantname": "K Kiosk Sihlquai","merchantstreet": "Sihlquai","addedtime": 1576590342000,"uniqueref": "A446806878486B5B0"
    },
    {"billingamountauthorised": "100","iconblob": "https://is1-ssl.mzstatic.com/image/thumb/Purple114/v4/cb/cf/bb/cbcfbb61-4d03-4f4e-ecf7-b7582688435f/source/512x512bb.jpg","merchantname": "K Kiosk Sihlquai","merchantstreet": "Sihlquai","addedtime": 1575554709000,"uniqueref": "0D10B5F56A73D73DD"
    },
    {"billingamountauthorised": "1320","iconblob": "https://pbs.twimg.com/profile_images/568401882444349441/KDWvUHCJ_400x400.jpeg","merchantname": "Schweizerische Bundesbahnen","merchantstreet": "Bahnhofplatz","addedtime": 1575554709000,"uniqueref": "2F3D907B0FF675216"
    }
  ]