DB2 "FIRST_DAY" function

DB2 comes with a lot of in-built functions. One of them is called LAST_DAY which returns the Last Day of a month, but there is no FIRST_DAY of the month function. Some of my colleagues asked about it. Here is an UDF (User Defined Function) that'll return FIRST DAY of the month:

CREATE FUNCTION schema.FIRST_DAY (IN_DATE DATE)
RETURNS DATE
LANGUAGE SQL
CONTAINS SQL
NO EXTERNAL ACTION
DETERMINISTIC
RETURN DATE(LAST_DAY(IN_DATE - 1 MONTH) + 1 DAY);