PostgreSQL: how to convert from Unix epoch to date? - sql

Question

The statement gives me the date and time.
How could I modify the statement so that it returns only the date (and not the time)?
SELECT to_timestamp( TRUNC( CAST( epoch_ms AS bigint ) / 1000 ) );

Answer 1

You use to_timestamp function and then cast the timestamp to date
select to_timestamp(epoch_column)::date;
You can use more standard cast instead of ::
select cast(to_timestamp(epoch_column) as date);
More details:
/* Current time */
select now(); -- returns timestamp
/* Epoch from current time;
Epoch is number of seconds since 1970-01-01 00:00:00+00 */
select extract(epoch from now());
/* Get back time from epoch */
-- Option 1 - use to_timestamp function
select to_timestamp( extract(epoch from now()));
-- Option 2 - add seconds to 'epoch'
select timestamp with time zone 'epoch'
+ extract(epoch from now()) * interval '1 second';
/* Cast timestamp to date */
-- Based on Option 1
select to_timestamp(extract(epoch from now()))::date;
-- Based on Option 2
select (timestamp with time zone 'epoch'
+ extract(epoch from now()) * interval '1 second')::date;
In your case:
select to_timestamp(epoch_ms / 1000)::date;
PostgreSQL Docs

Answer 2

select to_timestamp(cast(epoch_ms/1000 as bigint))::date
worked for me

Answer 3

On Postgres 10:
SELECT to_timestamp(CAST(epoch_ms as bigint)/1000)

Answer 4

The solution above not working for the latest version on PostgreSQL. I found this way to convert epoch time being stored in number and int column type is on PostgreSQL 13:
SELECT TIMESTAMP 'epoch' + (<table>.field::int) * INTERVAL '1 second' as started_on from <table>;
For more detail explanation, you can see here https://www.yodiw.com/convert-epoch-time-to-timestamp-in-postgresql/#more-214

Answer 5

This works for me fine:
SELECT t.*,
to_timestamp(cast(t.prev_fire_time/1000 as bigint)) as prev_fire_time,
to_timestamp(cast(t.next_fire_time/1000 as bigint)) as next_fire_time,
to_timestamp(cast(t.start_time/1000 as bigint)) as start_time
FROM public.qrtz_triggers t;

Answer 6

Seconds since epoch with GNU date:
$ date +%s.%N
1627059870.945134901
This works with PostgreSQL 11:
# select to_timestamp (1627059870.945134901);
to_timestamp
-------------------------------
2021-07-23 19:04:30.945135+02
(1 row)
# select to_timestamp (1627059870.945134901)::date;
to_timestamp
--------------
2021-07-23
(1 row)