App.js

import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
import { view, store } from '@risingstack/react-easy-state';
import moment from 'moment';

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  text: {
    fontSize: 40,
  },
});

function getFormattedTime() {
  return moment()
    .utc()
    .format('hh:mm:ss A');
}

class App extends React.Component {
  clock = store({ time: getFormattedTime() });

  componentDidMount() {
    this.interval = setInterval(
      () => (this.clock.time = getFormattedTime()),
      1000,
    );
  }

  componentWillUnmount() {
    clearInterval(this.interval);
  }

  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.text}>{this.clock.time}</Text>
      </View>
    );
  }
}

export default view(App);