mysql calculates the time difference function

MySql calculates the time difference between two dates
Grammar:
TIMESTAMPDIFF(interval,datetime_expr1,datetime_expr2)
Description:
Returns the integer difference between the date or date-time expressions datetime_expr1 and datetime_expr2the. As a result of
The units are given by the interval parameter. The legal value of interval is the same as listed in the TIMESTAMPADD() function description.

SELECT TIMESTAMPDIFF(MONTH,'2009-10-01','2009-09-01'); 
interval But:  
SECOND  seconds  SECONDS 
MINUTE  minutes  MINUTES 
HOUR  time  HOURS 
DAY  day  DAYS 
MONTH  month  MONTHS 
YEAR  years  YEARS