Entrypoint firstdayweek compatible with UTF-8
Input TIMESTAMP date optionally time Output TIMESTAMP Date with 1st day of (US)weekday (Sunday) as date with time 00:00:00
TestSQL SELECT '21.12.2008' AS ISCORRECT, F_FIRSTDAYWEEK('26.12.2008 15:00:00') FROM RDB$DATABASE; SELECT NULL AS ISCORRECT, F_FIRSTDAYWEEK(NULL) FROM RDB$DATABASE;