In PostgreSQL, timeofday() is a non-SQL-standard time function that returns the current date and time, with the time zone abbreviation.

It’s similar to the clock_timestamp() function, except that it returns its result as a formatted text string rather than a timestamp with time zone value. 

The result of both functions changes throughout the execution of a statement. Therefore, you could get a different result in different parts of the statement if you call the functions multiple times within a single statement.

In PostgreSQL, the localtime function returns the local time of the day, without the time zone offset.

If you need the time zone offset, use current_time() instead.

In PostgreSQL, the current_time function returns the current time, including the time zone offset.

The time returned is based on the start time of the current transaction.

In PostgreSQL, the current_date function returns the current date.

In PostgreSQL, the date_trunc() function truncates a date/time value to a specified precision.

It can also truncate the value to a specified precision in a specified time zone.

You could think of it as a date version of the trunc() function (which truncates numbers).

In PostgreSQL, you can use the timezone() function to convert a timestamp to another timezone.

In PostgreSQL, the current_timestamp() function returns the current date and time, including the time zone offset.

The timestamp returned is based on the start time of the current transaction.