DayPilotScheduler change date , Incorrect time!

my code:

<el-date-picker v-model="nowDay" @change="changeDate(0)"
        :picker-options="pickerOptions"
        type="date" format="yyyy 年 MM 月 dd 日"  size="small"></el-date-picker>


changeDate(dayNum){
      if (dayNum==0)  //select by date-picker
      {
        this.scheduler.startDate = this.nowDay;
      }
      else
      {
        this.nowDay =this.scheduler.startDate.addDays(dayNum);
        this.scheduler.startDate = this.nowDay;
      }
      this.config.startDate = this.nowDay;
      this.scheduler.update();
      
      console.warn('this.nowDay :'+this.nowDay)
      console.warn('this.scheduler.startDate :'+this.scheduler.startDate)
      console.warn('this.config.startDate :'+this.config.startDate)
    }