PostgreSQL: how to convert from Unix epoch to date?

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 ) );

Solution 1

You use to_timestamp function and then cast the timestamp to date

 select to_timestamp(epoch_column)::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

Solution 2

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

worked for me

Solution 3

On Postgres 10:

SELECT to_timestamp(CAST(epoch_ms as bigint)/1000)

Solution 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

Solution 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;

View more solutions

Comments

[cryanbhu]

doesn't seem to work, i get syntax error. Did it change as of 2018?

[cryanbhu]

well i ran the select to_timestamp(extract(epoch epoch_ms))::date; verbatim and it gave a syntax error near epoch_ms. I went to find other solutions and eventually this worked for me SELECT TIMESTAMP 'epoch' + (start_dt) * INTERVAL '1 second' as started_on. Could you please explain the difference between TIMESTAMP and to_timestamp()?

[Losbaltica]

TIMESTAMP is just column type where to_timestamp is a build in function that translates unix epoch to timestamp starting calculations from '1970-01-01 00:00:00+00'

[a_horse_with_no_name]

The above solutions will most definitely work with Postgres 12 or 13. But you can simplify your solution to make_timestamp(sec => the_column)

[Luc]

any idea how to make this work for older version (Postgres 8.0 / Redshift)?