LKD, 2005-2015 is eleven years if you are going to count the 2005 as one ie "first annual" event (wrongly, of course). If 2006 is the first annual (second event) then 2015 is the tenth annual.

Toy - it's the fifth annual discussion. You don't count the first year. Look at it this way - if I said See you next Monday and it's a Monday now, that's 8 days, not a week. If you're born January 1st then your next birthday is not a year - that would be December 31; it's 366 days. "A year ago today" is a misnomer - they incorrectly say 'a year' when in fact it's 366 days or even if it's ten years etc.

Same thing.

Technically the 'first annual' is the second event. So 11 years would be ten annual events. Can't start on zero (same as the millenium, etc).