Format option in vue-datetime wrong format

Use datetime format.
For example:

<datetime type="datetime" v-model="datetime13" format="yyyy-MM-dd HH:mm:ss"></datetime>

From the vue-datetime documentation here, It states that you need to use luxon and weekstart. Make sure you install the two packages like this npm install --save luxon vue-datetime weekstart.

Register your DateTime package globally or locally

Globally

import { Datetime } from 'vue-datetime';
 
Vue.component('datetime', Datetime);

Locally

import { Datetime } from 'vue-datetime';
 
Vue.extend({
  template: '...',
  components: {
    datetime: Datetime
  }
});

This vue-datetime use luxon to set date formats

<template>
<div>
  <datetime type="date"
  v-model="formData.testDate"
  input-class="form-control"
  :format="{ year: 'numeric', month: 'long', day: 'numeric' }">
  </datetime>

  <!-- Or use this -->

  <datetime type="date"
  v-model="formData.testDate"
  input-class="form-control"
  format="dd/MM/yyyy">
  </datetime>

</div>    
</template>

<script>
import { Datetime } from 'vue-datetime';
export default {
    data(){
        return {
            formData: {
                testDate: ''
            }
        }
    },
    components: {
        datetime: Datetime
    }
    
}
</script>

I hope my answer will be helpful

You are trying to apply a format to a string. The format should bind to a variable, the variable needs to reference the wanted format option of the DateTime module of luxon.

<template>
  <div id="app">
    <datetime type="date" v-model="formData.testDate" input-class="form-control" :format="format" />
  </div>
</template>

<script>
import { DateTime } from 'luxon';

export default {
  name: 'app',
  components: {
  },
  data: () => ({
    formData: {
      testDate: '',
    },
    format: DateTime.DATE_SHORT,
  }),
}
</script>

Use the luxon

npm install --save luxon

and

import { DateTime } from 'luxon';
...
//yourDateFromForm = '2019-06-27T11:06:00.000Z'
console.log(DateTime.fromISO(this.yourDateFromForm).toFormat('DD/MM/YYYY'))