Difference in months of date in postgresql

There is in PostgreSQL the function Age which, in my opinion, represents the difference between the dates. The SQL below also shows the result of difference of months between two dates:

SELECT ((ANOS * 12) + MESES) AS MESES
FROM 
(
  SELECT 
    CAST(TO_CHAR(AGE(data2, data1),'YY') AS INTEGER) AS ANOS,
    CAST(TO_CHAR(AGE(data2, data1),'MM') AS INTEGER) AS MESES, 
    CAST(TO_CHAR(AGE(data2, data1),'DD') AS INTEGER) AS DIAS
  FROM tabela
) AS tabela

SQLFiddle

You can get the value in months by extracting the parts manually and doing the math operations involved. Unfortunately, PostgreSQL does not have a DATEDIFF function to simplify these calculations:

  SELECT (DATE_PART('year', data2) - DATE_PART('year', data1)) * 12 
         + (DATE_PART('month', data2) - DATE_PART('month', data1));

Sources:

PostgreSQL - DATEDIFF - Datetime Difference in Seconds, Days, Months, Weeks etc. - SQLines
• PostgreSQL Wiki - Working with Dates and Times in PostgreSQL

If only the integer number of months is required:

select
    (
        select count(*) - 1
        from generate_series(date1, date2, '1 month')
    ) as meses
from (values
    ('2013-03-16'::date, '2014-07-16'::date)
) g (date1, date2)
;
 meses 
-------
    16