Doing some research I came across the fact that in the USA there are two days set aside as National Miniature Days!
According to Wikipedia National Miniature Golf Day is held every second Saturday of May. The event had its inaugural celebration on May 12, 2007 and this year will fall on the 8th May.
Also, according to the Holiday Insights website Miniature Golf Day is "Always September 21st"!
In 2010 the 21st of September is a Tuesday.
Looking forward to celebrating all things Miniature Golf on both days!