解决:用blur 替代 change
<el-date-picker @blur="changeTime" v-model="form.time" type="daterange" range-separator="至" start-placeholder="开始日期" end-placeholder="结束日期" value-format="yyyy-MM-dd" format="yyyy-MM-dd" ></el-date-picker>
changeTime() {
this.$forceUpdate();
},