PostgreSQL NOW Function

Summary: this tutorial shows you how to use the PostgreSQL NOW() function to get the date and time with time zone.

Introduction to PostgreSQL NOW() function

The NOW() function returns the current date and time. The return type of the NOW() function is the timestamp with time zone. See the following example:

SELECT NOW();
              now
-------------------------------
 2017-03-18 08:21:36.175627+07
(1 row) 
Code language: SQL (Structured Query Language) (sql)

Note that the NOW() function returns current date and time based on the database server’s time zone setting.

For example, if we change the timezone to ‘America/Los_Angeles’:

SET TIMEZONE='America/Los_angeles';
Code language: SQL (Structured Query Language) (sql)

And get the current date and time:

SELECT NOW();
              now
-------------------------------
 2017-03-17 18:29:21.758315-07
(1 row)
Code language: SQL (Structured Query Language) (sql)

As you can see, the value returned by the NOW() function is adjusted to the new timezone.

If you want get the current date and time without timezone, you can cast it explicitly as follows:

SELECT NOW()::timestamp;
            now
----------------------------
 2017-03-17 18:37:29.229991
(1 row)
Code language: SQL (Structured Query Language) (sql)

You can use the common date and time operator to the NOW() function. For example, to get 1 hour from now:

SELECT (NOW() + interval '1 hour') AS an_hour_later;
         an_hour_later
-------------------------------
 2017-03-17 19:42:37.110567-07
(1 row)
Code language: SQL (Structured Query Language) (sql)

To get this time tomorrow, you add 1 day to the current time:

SELECT (NOW() + interval '1 day') AS this_time_tomorrow;
      this_time_tomorrow
-------------------------------
 2017-03-17 19:43:35.178882-07
(1 row)
Code language: SQL (Structured Query Language) (sql)

To get 2 hours 30 minutes ago, you use the minus (-) operator as follows:

SELECT now() - interval '2 hours 30 minutes' AS two_hour_30_min_go;

      two_hour_30_min_go
-------------------------------
 2017-03-17 16:17:07.742688-07
(1 row)
Code language: SQL (Structured Query Language) (sql)

PostgreSQL NOW() related functions

Besides the NOW() function, you can use the CURRENT_TIME or CURRENT_TIMESTAMP to get the current date and time with timezone:

SELECT CURRENT_TIME, CURRENT_TIMESTAMP;
       timetz       |              now
--------------------+-------------------------------
 18:50:51.191353-07 | 2017-03-17 18:50:51.191353-07
(1 row)
Code language: SQL (Structured Query Language) (sql)

To get the current date and time without time zone, you use the LOCALTIME and LOCALTIMESTAMP functions.

SELECT LOCALTIME, LOCALTIMESTAMP;
      time       |         timestamp
-----------------+----------------------------
 19:13:41.423371 | 2017-03-17 19:13:41.423371
(1 row)
Code language: SQL (Structured Query Language) (sql)

Notice that NOW() and its related functions return the start time of the current transaction. In other words, the return values of the function calls are the same within a transaction.

The following example illustrates the concept:

postgres=# BEGIN;
BEGIN
postgres=# SELECT now();
              now
-------------------------------
 2017-03-17 19:21:43.049715-07
(1 row)


postgres=# SELECT pg_sleep(3);
 pg_sleep
----------

(1 row)


postgres=# SELECT now();
              now
-------------------------------
 2017-03-17 19:21:43.049715-07
(1 row)


postgres=# COMMIT;
COMMIT
Code language: SQL (Structured Query Language) (sql)

In this example, we called the NOW() function within a transaction and as you can see its return values do not change through the transaction.

Note that the pg_sleep() function pauses the current session’s process sleep a specified of seconds.

If you want to get the current date and time that does advance during the transaction, you can use the TIMEOFDAY() function. Consider the following example:

SELECT 
    TIMEOFDAY(), 
    pg_sleep(5), 
    TIMEOFDAY();
              timeofday              | pg_sleep |              timeofday
-------------------------------------+----------+-------------------------------------
 Fri Mar 17 19:36:09.216064 2017 PDT |          | Fri Mar 17 19:36:14.217636 2017 PDT
(1 row)
Code language: SQL (Structured Query Language) (sql)

As you see, after pausing 5 seconds, the current date and time increased.

PostgreSQL NOW() function as default values

You can use the NOW() function as the default value for a column of a table. See the following example:

First, create a new table named posts with the created_at column that has a default value provided by the NOW() function:

CREATE TABLE posts ( 
     id         SERIAL PRIMARY KEY, 
     title      VARCHAR NOT NULL, 
     created_at TIMESTAMPTZ DEFAULT Now() 
);
Code language: SQL (Structured Query Language) (sql)

Second, insert a new row into the posts table:

INSERT INTO posts (title) 
VALUES     ('PostgreSQL NOW function');
Code language: SQL (Structured Query Language) (sql)

Third, query data from the posts table:

SELECT * FROM posts;

 id |          title          |          created_at
----+-------------------------+-------------------------------
  1 | PostgreSQL NOW function | 2017-03-18 09:41:26.208497+07
(1 row)
Code language: SQL (Structured Query Language) (sql)

Even though we did not provide the value for the created_at column, the statement used the value returned by the NOW() function for that column.

In this tutorial, you have learned how to use the PostgreSQL NOW() function to get the current date and time with timezone.