SOURCE

var Main = {
  data() {
    return {
      value: ''
    }
  },
  watch: {
    value (newVal, oldVal) {
      console.log('xxxx', new Date(newVal))
    }
  } 
}
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui/lib/index.js"></script>
<div id="app">
  <el-time-picker
                  style='width: 140px'
                  v-model="value"
                  format="HH:mm"
                  value-format="timestamp"
                  :picker-options="{
                    selectableRange: '00:00:00 - 23:59:59'
                  }"
                  placeholder="开始时间"
                  >
                </el-time-picker>
</div>

@import url("//unpkg.com/element-ui/lib/theme-chalk/index.css");