Count months between two timestamp on postgresql?

Question

I want to count the number of months between two dates.

Doing :

SELECT TIMESTAMP \'2012-06-13 10:38:40\' - TIMESTAMP \'2011-04-30 14:38:40\';


        

Answer 1

If you will do this multiple times, you could define the following function:

CREATE FUNCTION months_between (t_start timestamp, t_end timestamp)
    RETURNS integer
    AS $$
        SELECT
            (
                12 * extract('years' from a.i) + extract('months' from a.i)
            )::integer
        from (
            values (justify_interval($2 - $1))
        ) as a (i)
    $$
    LANGUAGE SQL
    IMMUTABLE
    RETURNS NULL ON NULL INPUT;

so that you can then just

SELECT months_between('2015-01-01', now());

Answer 2

Try;

select extract(month from  age('2012-06-13 10:38:40'::timestamp, '2011-04-30 14:38:40'::timestamp)) as my_months; 

Answer 3

I had the same problem once upon a time and wrote this ... it's quite ugly:

postgres=>  SELECT floor((extract(EPOCH FROM TIMESTAMP '2012-06-13 10:38:40' ) - extract(EPOCH FROM TIMESTAMP '2005-04-30 14:38:40' ))/30.43/24/3600);
 floor 
-------
    85
(1 row)

In this solution "one month" is defined to be 30.43 days long, so it may give some unexpected results over shorter timespans.

Answer 4

Extract by year and months will floor on months:

select extract(year from age('2016-11-30'::timestamp, '2015-10-15'::timestamp)); --> 1
select extract(month from age('2016-11-30'::timestamp, '2015-10-15'::timestamp)); --> 1
--> Total 13 months

This approach maintains fractions of months (thanks to tobixen for the divisor)

select round(('2016-11-30'::date - '2015-10-15'::date)::numeric /30.43, 1); --> 13.5 months

Answer 5

Gives the differenece of months of two dates

   SELECT ((extract( year FROM TIMESTAMP '2012-06-13 10:38:40' ) - extract( year FROM TIMESTAMP '2011-04-30 14:38:40' )) *12) + extract(MONTH FROM TIMESTAMP '2012-06-13 10:38:40' ) - extract(MONTH FROM TIMESTAMP '2011-04-30 14:38:40' );

The Result : 14

Have to extract months seperately for both the dates and then the difference of both the results

Answer 6

The age function give a justified interval to work with:

SELECT age(TIMESTAMP '2012-06-13 10:38:40', TIMESTAMP '2011-04-30 14:38:40');

returns 1 year 1 mon 12 days 20:00:00, and with that you can easily use EXTRACT to count the number of months:

SELECT EXTRACT(YEAR FROM age) * 12 + EXTRACT(MONTH FROM age) AS months_between
FROM age(TIMESTAMP '2012-06-13 10:38:40', TIMESTAMP '2011-04-30 14:38:40') AS t(age);