Make wp_tag_cloud know when a tag is outdated

So currently as I understand it, the wp_tag_cloud displays the most popular tags by how many posts are associated with that tag.

I run a news site and I tag posts with the incident it relates to. So for example I currently have 5 stories with the giffords shooting tab, which makes it the biggest tag.

The problem is that in about 2 months when there is no more news on Giffords, the Giffords shooting tag will still show up in the Tag cloud because it has 5 tags.

Is there a way to make wp_tag_cloud know when the last time a post was made with a certain tag, and to remove it from the cloud display if there hasn’t been a new post with that tag in a specific amount of time?