Vue

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.6.6/vue.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>
<div id="app">
{{testTime}}

<button @click=onClick>click</button>
</div>

Babel + JSX

new Vue({
  el: "#app",
  data: {
  		testTime: 12
  },
  
  mounted(){
  	this.testTime =  moment().format('DD.MM.YYYY'); 
  },
  methods: {
    onClick(){
  	this.testTime =  moment().format('YYYY.MM.DD'); 
    }
  }
});