Not to get too picky with this but I think it's a little obvious that 2010 is the 20th year of Harbour Lights.

If 1991 was the 1st year it's pretty simple to figure. The last digit of the year lines up. 91=1, 92=2, 93=3, etc. Then 2000 was the 10th year, then 2009 is the 19th year, so 2010 is the 20th year for collecting HL's!

1st year 1991
2nd year 1992
3rd year 1993
4th year 1994
5th year 1995
6th year 1996
7th year 1997
8th year 1998
9th year 1999
10th year 2000
11th year 2001
12th year 2002
13th year 2003
14th year 2004
15th year 2005
16th year 2006
17th year 2007
18th year 2008
19th year 2009
20th year 2010

Of course, that doesn't mean HL can't wait till the 20th year is history to have an anniversary in 2011, the 21st year of production.

I know, I know, this is getting a little too detailed !!! Just doing it for clarification.