Oracle SQL: Difference between two dates in minutes

[Guru]

I have a date field containing date and time.

How do I calculate the difference in minutes between this date and sysdate?






Thanks

[Ecniv]

select inst.thedate,
  instr(inst.thedate,':') FirstOne,
  instr(inst.thedate,':',instr(inst.thedate,':')+1) SecondOne,
  substr(Inst.thedate,instr(inst.thedate,':')-2,2) TheHours,
  substr(Inst.thedate,instr(inst.thedate,':')+1,2) TheMins,
  substr(Inst.thedate,instr(inst.thedate,':',instr(inst.thedate,':')+1)+1,2) TheSecs,
  to_number(substr(Inst.thedate,instr(inst.thedate,':')-2,2))*60 + to_number(substr(Inst.thedate,instr(inst.thedate,':')+1,2)) TheTotalMins
From 
(select to_char(localtimestamp-to_timestamp('28-jul-05 12.20.53.466428')) thedate 
from tablename 
where tablename.id=1048) Inst

The long way.
I expect there is a function somewhere in Oracle that does it, but I couldn't see it straight off.

Edit:
Also found an Extract function - although I couldn't get it to work.