表單驗證validate，element的日期選擇使用value-format之后表單驗證報錯

element日期控件在表單驗證時報錯：Error in event handler for "el.form.change": "TypeError: value.getTime is not a function"

<el-form-item label="生效日期" prop="StartDate"><el-date-picker v-model="addForm.StartDate" value-format="yyyy-MM-dd" type="date" placeholder="選擇生效日期"></el-date-picker>
</el-form-item>

StartDate: [{ type: 'date', required: true, message: '請選擇生效日期', trigger: 'change' }]

解決：
表單驗證將 type:'date' 改為 type:'string'

StartDate: [{ type: 'string', required: true, message: '請選擇生效日期', trigger: 'change' }],