vue computed setter e getter

exemple.vue

<template>
  <v-date-picker v-model="formattedDate">
</template>
<script>
export default {
  data: function () {
    return { date: '2018-MAY-09T12:00:00' }
  },
  computed: {
    formattedDate: {
      get() { return /* transfor this.date here */  },
      set(valueFromPicker) { this.date = /* transform back here */ }
    }
  }
}
</script>