Hello @god_prophet
You will have to use a javascript code before uploading the file to check if the file date is before today or not.
The code to get the modified date of a file is this:
var PATH=getOption("SFTP_UploadFolder");
var FOLDER_PATH=PATH+"/FILE_NAME.csv";
var myFile = new File(FOLDER_PATH);
logInfo(myFile.lastModified); // this will return the modified date