Fine! The query worked this time.

Intervals are typically used with the comparison operators (e.g. >, >=) to select facts from a given day, month, year etc. Take a look:

SELECT id
FROM aircraft
WHERE produced >= '2010-01-01'
  AND produced < CAST('2010-01-01' AS date) + INTERVAL '1' YEAR;

The above query will look for aircraft produced in 2010. Note that we needed to use CAST when adding an interval.