Date Time Functions - ANSI SQL ?

Curious to know...

Are all the date time functions described in the pgSQL docs are ANSI-SQL or pgSQL extensions?

For Example in the Docs:
------------------------
4.7.1. EXTRACT, date_part

EXTRACT (field FROM source)

The extract function retrieves sub-fields from date/time values, such as year or hour. source is a value expression
thatevaluates to type timestamp or interval. (Expressions of type date or time will be cast to timestamp and can
thereforebe used as well.) field is an identifier (not a string!) that selects what field to extract from the source
value.The extract function returns values of type double precision. The following are valid values: 
 

day The day (of the month) field (1 - 31) 
 SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 16

Thanks all,