gistfile1.php

<?php
// ......
                $value = $this->_ExcelData->sheets[ 0 ][ 'cells' ][ $i ][ $j ];
                $type = $this->_TableField[ $j - 1 ][ 'type' ];
// ......                
                elseif ( preg_match( '/(date|datetime|timestamp)/', $type ) )
                {
                    // date verification assume dd-mm-yyyy format
                    if ( preg_match( '/[0-9]{1,2}(\-|\/)[0-9]{1,2}(\-|\/)[0-9]{2,4}/', $value ) )
                    {
                        $cell_info = $this->_ExcelData->sheets[ 0 ][ 'cellsInfo' ][ $i ][ $j ];               
                        if ( 'date' == $cell_info[ 'type' ] )
                        {
                            $valid = true;
                            
                            $value = $cell_info[ 'raw' ];
                            $value = date( 'Y-m-d', $value );
                            $value = strtotime( "$value - 1 day ago" );
                            $value = date( 'Y-m-d', $value );
                        }
                        else
                        {
                            // dates stored as string (') in excel
                            // will handle dd-mm-yyyy or dd/mm/yyyy
                            $datesplit = preg_split( '/(\-|\/)/', $value );
                            $day = $datesplit[ 0 ];
                            $month = $datesplit[ 1 ];
                            $year = $datesplit[ 2 ];
    
                            if ( checkdate( $month, $day, $year ) )
                            {
                                $valid = true;
                                
                                $value = $year . '-' . $month . '-' . $day;
                            }
                            else
                            {
                                $this->_Error = 741;
                                $this->_ErrorText[] = 'Data at row ' . $i . 'col ' . $j . ' is not a valid date ' . $day . '-' . $month . '-' . $year . '. ' . $this->_Error;
                            }
                        }
                    }
                    elseif ( is_numeric( $value ) )
                    {
                        $valid = true;
                        $basedate = 'January 1, 1900';
                        
                        // for some reason excel stores dates as an integer reckoned from January 1, 1900 minus two days.
                        // will handle integers
                        $value -= 2;
                        $value = strtotime( "$basedate + $value days" );
                        $value = date( 'Y-m-d', $value );
                    }
                    else
                    {
                        $this->_Error = 742;
                        $this->_ErrorText[] = 'Data at row ' . $i . 'col ' . $j . ' does not have the correct date format (dd-mm-yyyy) ' . $day . '-' . $month . '-' . $year . '. ' . $this->_Error;
                    }
                }
// ......