$values = []; $cellData = new Google_Service_Sheets_CellData(); $value = new Google_Service_Sheets_ExtendedValue(); $value->setStringValue($aDateS->format("dmY")); // $aDateS -> DateTime object $cellData->setUserEnteredValue($value); $values[] = $cellData; $rowData = new Google_Service_Sheets_RowData(); $rowData->setValues($values); $rows[] = $rowData; Next, I create a query:
$appendRequest->setSheetId($aSheetId); $appendRequest->setRows($rowAr); $appendRequest->setFields("userEnteredValue"); $request = new Google_Service_Sheets_Request(); $request->setAppendCells($appendRequest); $requests = [$request]; $batchUpdateRequest = new Google_Service_Sheets_BatchUpdateSpreadsheetRequest(["requests" => $requests]); And I send it, it is successfully sent, but before the date itself, for some reason, it inserts a 'quote 
Other values are normally inserted.