timestamp and date math and functions are an important concept to master in the FM universe
Basically timestamp ( future ) - timestamp (past) returns the number of seconds difference. You can then parse this number into its individual components with the functions.
A simply date - date calc will give a result in days: e.g. GetAsDate ( "12/05/2017" ) - GetAsDate ( "12/03/2017" ) = 61.
If you only need to know days remaining this would suffice. A result in years months and days is more complicated and not necessarily the same.
you can calculate the date difference abd you can have a portal to show the records that are due to expire eg <=30 days so you will know or have 2 portals <=60 and <=30 etc
And then you can have a script to check witch ones are expiring and automate an email notification