Commented by: @mrotteveel

The reason we don't have it, is probably that it is not defined in the standard (at least, not in SQL:2011). As a workaround, the quarter can be trivially derived using:

1 + (extract(MONTH from somevalue) - 1) / 3

Commented by: @asfernandes

What others DBMS has this?

Oracle: select to_char(sysdate, 'Q') as qtr from dual;
MSSQL: SELECT DATEPART(quarter, '2017/08/25') AS DatePartInt;
Mysql: SELECT QUARTER("2017-06-15");
Postre: SELECT EXTRACT (QUARTER FROM TIMESTAMP '2011-11-22 13:30:15')

Extract would also be logical for Firebird:
select extract(quarter from cast('TODAY' as date)) from rdb$database