MySQL two time subtract after take minutes

Case when Timestampdiff (minute,o.createdate,o.chargingstartdate)!= the Then'App Unlocking billing'ELSE'Automatic system Billing'Endtimestampdiff (minute,o.createdate,o.chargingstartdate)  O.chargingstartdate minus o.createdate Subtracts the minutes, if the latter is less than the first minute is a negative number. SELECT Timestampdiff (MONTH,'2009-10-01','2009-09-01'); Interval but: SECOND seconds SECONDS MINUTE minutes MINUTES HOUR time HOURS day days months month MONTHS year yearsSelectID, Createdate,now (), MINUTE (Timediff (now (), createdate)) fromT_base_task limitTen

MySQL takes minutes after subtracting between two times