// create a variable that accesses all tabs of my spreadsheet
var ss = SpreadsheetApp.getActiveSheet();
// create a variable that contains the first sheet
var sheet = ss.getSheets()[0];
// insert a new column (not zero-indexed like the line above)
sheet.insertColumnBefore(2);
// add the date to the column
var date = Utilities.formatDate(new Date(), "GMT-4", "dd/MM/yyyy");
sheet.getRange('B2').setValue(date);