rman script

 If anyone can point what I'm doing wrong to get this error in my recovery script I would appreciate it.  I can't see the error.
RMAN> run{
2> set until time "to_date('2009-12-09 12:50:00' , 'yyyy-mm-dd hh:mm:ss')";
3> alter database mount;
4> restore database;
5> recover database;
6> alter database open resetlogs;
7> }

executing command: SET until clause
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of set command at 12/10/2009 12:02:03
ORA-00907: missing right parenthesis


thanks