How to detect which files need an update

[Ton Cardona]

One program of mine is based on compressed files which the user 
downloads from an FTP to his hard disk. Those files are frequently 
updated (legal stuff).

Although it is easy to detect the date of files in the FTP, I am unable 
to detect whether the files in the hard disk do need an update by 
comparing their dates to the dates of those in the FTP.

Thanks in advance for any ideas.

Ton Cardona