Tracking skill expiration dates

Hi, 

I'm trying to figure out how to track the expiration dates for the skills & certificates of our users, where can I set that up so I can run a report or have a report auto-generate on a schedule to allow me to monitor such information? 

for example, a user has a certificate that expires next May. How can I track that and have a report generated maybe 2-3 months in advance that will show me this info?

Thanks!