CURRENT_TIMESTAMP Function - SQL Server to PostgreSQL Migration

In SQL Server, the CURRENT_TIMESTAMP function returns the current date and time with milliseconds precision without the time zone for the database server's host operating system.

CURRENT_TIMESTAMP returns the actual current date and time, but SQL Server can optimize how many times it is evaluated within a statement (run-time constant).

In PostgreSQL you can use the CLOCK_TIMESTAMP function, which also returns the actual current date and time, or the CURRENT_TIMESTAMP(3) function, which returns the start of the current transaction.

Note that PostgreSQL functions use the client's session time zone.

SQL Server:

  -- Get the current date and time with milliseconds precision
  SELECT CURRENT_TIMESTAMP;
  /* 2026-08-08 17:43:36.913 */

PostgreSQL:

  -- Get the current date and time with milliseconds precision
  SELECT CLOCK_TIMESTAMP()::TIMESTAMP(3);
  /* 2026-08-08 17:43:36.913 */
 
  -- Without a cast to TIMESTAMP(3), CLOCK_TIMESTAMP uses microseconds precision and includes the time zone
  SELECT CLOCK_TIMESTAMP();
  /* 2026-08-08 17:43:36.913794-07 */
 
  -- CURRENT_TIMESTAMP uses microseconds precision by default and includes the time zone
  SELECT CURRENT_TIMESTAMP, CURRENT_TIMESTAMP(3);
  /* 2026-08-08 17:44:37.850512-07 | 2026-08-08 17:44:37.851-07 */

Unlike SQL Server, where CURRENT_TIMESTAMP returns the actual current date and time, in PostgreSQL it returns the start date and time of the current transaction.

SQL Server:

  -- Start a new transaction
  BEGIN TRANSACTION
 
  -- Get the current date and time
  SELECT CURRENT_TIMESTAMP;
  /* 2026-08-08 18:08:26.030 */
 
  -- Wait 3 seconds
  WAITFOR DELAY '00:00:03'
 
  -- Get the current date and time again (reflects the 3-second wait)
  SELECT CURRENT_TIMESTAMP;
  /* 2026-08-08 18:08:29.030 */ 
 
  COMMIT;

PostgreSQL:

  -- Start a new transaction
  BEGIN;
 
  -- Get the current date and time
  SELECT CLOCK_TIMESTAMP(), CURRENT_TIMESTAMP;
  /* 2026-08-08 08:21:42.82698-07 | 2026-08-08 08:21:42.823941-07 */
 
  -- Wait 3 seconds
  SELECT PG_SLEEP(3);
 
  -- Get the current date and time again (Only CLOCK_TIMESTAMP reflects the 3-second wait)
  SELECT CLOCK_TIMESTAMP(), CURRENT_TIMESTAMP;
  /* 2026-08-08 08:21:45.886739-07 | 2026-08-08 08:21:42.823941-07 */ 
 
  COMMIT;

You can see that within the same transaction, PostgreSQL CURRENT_TIMESTAMP always returns the same value regardless of the transaction's duration. This might not always be the desired behavior.

In SQL Server, CURRENT_TIMESTAMP always uses the server instance time zone, while PostgreSQL functions use the client's session time zone.

PostgreSQL:

  -- Get the current time zone
  SHOW TIMEZONE;
  /* America/Los_Angeles */
 
  -- Get the current date and time
  SELECT CLOCK_TIMESTAMP(), CURRENT_TIMESTAMP;
  /* 2026-08-08 08:37:56.774409-07 | 2026-08-08 08:37:56.774334-07 */
 
  -- Change the client's time zone
  SET SESSION TIME ZONE 'America/New_York';
 
  -- Now functions return date and time in the new time zone
  SELECT CLOCK_TIMESTAMP(), CURRENT_TIMESTAMP;
  /* 2026-08-08 11:39:07.075324-04 | 2026-08-08 11:39:07.075248-04 */

For more information, see SQL Server to PostgreSQL Migration.