In download file name you can not use / caracther you can use -
For today date i use this
{
"Command": "executeScript_Sandbox",
"Target": "var d = new Date();var m = ((d.getMonth()+1)<10) ? \"0\" + (d.getMonth()+1):(d.getMonth()+1);var day=d.getDate()<10 ? \"0\" + d.getDate():d.getDate();return day + \"-\" + m + \"-\" + d.getFullYear();",
"Value": "Date"
},