2018-03-25: {
   title: 'Some title',
   description: 'Some description',
   start: {
      dateTime: '2018-03-25T08:00:00+02:00',
   },
   end: {
      dateTime: '2018-03-25T09:45:00+02:00'
   }
},
2018-03-25: {
   title: 'Some title2',
   description: 'Some description2',
   start: {
      dateTime: '2018-03-25T10:00:00+02:00',
   },
   end: {
      dateTime: '2018-03-25T13:00:00+02:00'
   }
}

fetch(url)
  .then((resp) => resp.json())
  .then((data) => {
     const events = data.items;
     if (events.length == 0) {
        console.log('No upcoming events found');
     }else {
        for (let i = 0; i < events.length; i++) {
           const event = events[i];
           const sTime = event.start.dateTime || event.start.date;
           const eTime = event.end.dateTime || event.end.date;
           const csTime = moment(sTime).format('YYYY-MM-DD');
           const ceTime = moment(eTime).format('YYYY-MM-DD');
           const csTime2 = moment(sTime).format('LT');
           const ceTime2 = moment(eTime).format('LT');
           if (!this.state.calItems[csTime]) {
              this.state.calItems[csTime] = [];
              this.state.calItems[csTime].push({
                  title: event.summary,
                  startTime: csTime2,
                  endTime: ceTime2,
                  description: event.description
              })
           }
        }
        console.log('Items: ' + JSON.stringify(this.state.calItems));
     }
  })
  .catch((error) => {
      console.log(error);
  })

2018-03-25: {
   title: 'Some title',
   description: 'Some description',
   start: {
      dateTime: '2018-03-25T08:00:00+02:00',
   },
   end: {
      dateTime: '2018-03-25T09:45:00+02:00'
   },
   title: 'Some title2',
   description: 'Some description2',
   start: {
      dateTime: '2018-03-25T10:00:00+02:00',
   },
   end: {
      dateTime: '2018-03-25T13:00:00+02:00'
   }
}