In PostgreSQL, difference between two timestamps in minutes can be calculated by providing the EPOCH as a sub-field to the EXTRACT function, and the result from the EXTRACT will be divided by 60 to get the minutes.
Example
SELECT EXTRACT(EPOCH FROM ((NOW() + interval '1 day')::TIMESTAMPZ - NOW())) / 60 AS minutes
SELECT EXTRACT(EPOCH FROM (end_date - start_date)) / 60 AS minutes