PhpExcel Cell格式：如何检测字符串和日期时间格式？

I am looking to validate the date and time format while reading excel file. Which some times can be without any excel format (date, number), etc. When someone puts characters like "bbb" instead of date 12-05-2018 06:24:23. It converts that data to today's date or servers initial date (43435.093935185).

Which is wrong, how can we detect if provided value in a cell is string or date?

I have already tried cell format function getCellByColumnAndRow($col,$row)

But it doesn't help to detect if data is valid or not as an end result is number only which is the valid date as such.

$data = $objWorksheet->getCellByColumnAndRow($col, $row);   

if(!strtotime($data)) {
    if(PHPExcel_Shared_Date::isDateTime($data)) {
        $cellValue = $objWorksheet->getCellByColumnAndRow($col, $row)->getValue();
        $dateValue = PHPExcel_Shared_Date::ExcelToPHP($cellValue);                       
        $dateh     = date('Y-m-d',$dateValue);                          
    } else {                        
        $dateh  = "";                                                   
    } else {
        $START_DATE = strtotime($data);
        $dateh = date('Y-m-d',$START_DATE);                         

    }               
}

$START_DATE = date('Y-m-d', PHPExcel_Shared_Date::ExcelToPHP($worksheet->getCellByColumnAndRow(1, $row)->getValue()));

I am looking to add the date in dB only if it's valid else provide an error message,