I've this placed in my .htaccess

Options +Indexes 
IndexOptions -FancyIndexing 

but despite -fancyindexing, it shows the alteration time. How can you disable this?

thanks

In my opinion you would like (From Apache's paperwork on IndexOptions):

IndexOptions SuppressLastModified

Documentation states:

This can suppress the display from the last modification date, in fancy indexing entries.

So you'll most likely want fancy indexing switched on to possess the work properly.