Show dates older than current date in sql query

Show dates older than current date in sql query

In my sql statement I have an SQL statement which i need to show which
customers return dates are overdue i.e. older than current date, so far my
query looks like the following:
SELECT customers.firstname, items.itemname, CustEquipment.ReturnDate,
customers.phonenumber
FROM items, CustEquipment, customers
WHERE items.ItemId = CustEquipment.ItemId AND
CustEquipment.customerID=customers.customerID;
This currently shows all customers and their return dates (along with
other info i need) but i want to show the return dates which have gone
past the current date, anyone care to point me in the right direction
please?