vxe-utils

npm install vxe-utils xe-utils

<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<script src="https://cdn.jsdelivr.net/npm/xe-utils"></script>
<script src="https://cdn.jsdelivr.net/npm/vxe-utils"></script>

import Vue from 'vue'
import XEUtils from 'xe-utils'
import VXEUtils from 'vxe-utils'

Vue.use(VXEUtils, XEUtils, { mounts: ['cookie'] })

<template>
  <h1>{{ userName }}</h1>
  <div>{{ $utils.toDateString(startDate, 'yyyy-dd-MM HH:mm:ss') }}</div>
  <div>{{ endDate }}</div>
</template>

<script>
export default {
  data() {
    return {
      userName: null,
      startDate: new Date(),
      endDate: null
    }
  },
  created() {
    this.userName = this.$cookie('U_NAME')
    this.endDate = this.$utils.toDateString(new Date(), 'MM/dd/yyyy HH:mm:ss.SSS')
  }
}
</script>