PSQL - Group Rows with timestamp interval

group_by_intervals_postgres.sql

-- POSTGRES SQL. 
-- Count of rows where a timestamp column falls in interval. 
-- This example uses a 5 minute interval ( 300 seconds = 5 minutes).
-- You need to replace the things inside square brackets, i.e. provide
-- the name of the table and timestamp column.
SELECT COUNT(*) cnt, 
to_timestamp(floor((extract('epoch' from [Timestamp Column]) / 300 )) * 300) 
AT TIME ZONE 'UTC' as expiry_interval
FROM [Table] GROUP BY expiry_interval
order by expiry_interval

Smart idea of generating the same marker for all the timestamp within the same interval.