Quick question about changing attributes on date?

I have set up a simple ‘ideas’ engine for my CMS where users accept an
idea and then have 14 days to do it. I have set all this up and it even
informs users how long they have left but i was wondering what the best
way to make the idea ‘expire’ is?

I have a field for the ‘do by’ date but once it gets past this the
number just continue going up. Ideally i need a way to change an
attribute in the row to return the idea to the pot as it were. I have
googled a few things but didn’t really know what it was called.

Is this do-able?

Thanks in advance,