added item table and installed whenever gem

Can you look at my table, I think I did it ok.  The date that is there is just a place holder.  I am having trouble trying to figure out how to get the date to tick down and then eventually auto remove.  I know we will use cron jobs to do it but I am a bit lost with that.  So first how do I get the date to change every say 24 hours and display in the list?  Also I will want to connect the checkbox to a update button so when checked you click update and it can manually remove the item.