Look at: Unable to upload file from local it may help you. To change date you can use runScript command to take date in specific format and join it with rest of the name of your file using JS as well. So JS inside runScript command should be something like:
var date = getDate in format (yyyymmdd)
return nameOfFile = “Name_”+date+"_Number"
So each day you play this test, name of your file will contain proper actual date.