Cron Job Help

Hello, I need some help on how to download a file using a cron job. I need to download a file from an ftp address on a separate server from where the cron job will run, get the file and put it in a particular directory on the server. In addition I only want to download the file if the ftp version is newer than the version on my server. I am currently doing the following which imports correctly but does not successfully check to see if the file is newer:
wget ftp://ftpaddress/data/item_import_prod_features.txt -O /home/serveraddress/item_import_prod_features.txt
Could someone tell me how I can do that please?