Entrypoint tzvalue_to_utc compatible with UTF-8
Input none Output DOUBLE Diff of local datetime to UTC (universal time code) in hours
TestSQL SELECT CAST(DATEDIFF(MINUTE, CURRENT_TIMESTAMP, F_LOCAL2UTC(CURRENT_TIMESTAMP)) / 60 AS DOUBLE PRECISION) AS ISCORRECT, F_TZVALUETOUTC() FROM RDB$DATABASE