First date to count for the 10 years period

[ngdqukhai]

Hi all,
I'm not quite how to determine the starting date of my 10 years. It said on UKBA that 10 years start either (1) the date you entered UK or (2) the date you were granted the visa.
Is there any rule to say which one we should use? I was granted my first UK visa on 20/08/2010 and entered UK on 19/09/2010.
Can I use 20/08/2010 as the starting date to count for my 10 years period?
My current visa will expire on 14/08 and it's definitely that I can not use the first day to enter UK as my starting point.
If I use the date of being granted visa, then I will be eligible to apply on 24/07 and still stay within my current visa time.
Thanks in advance.

[seagul]

and entered UK on 19/09/2010.

Above date will be considered in case of long residence application.