On Tuesday, May 18, 2010, In celebration of their 50th birthday, Haagen-Dazs will celebrate 50 years as the first super premium ice cream with its annual Free Flavor Day.  From 4:00 p.m. to 8:00 p.m. in any participating Haagen-Dazs Shop across the country, ice cream lovers can wish the brand a “Happy Birthday” and enjoy…