Les Casques blues, sometimes referred to in English as the Blue Berets (in reference to the light blue color of their helmets), first saw service in 1948 in Palestine during the UN's first official peacekeeping mission.
Today these volunteers number more than 120,000 and serve on four continents. Since it's inception, the traditional role of the Casques blues has evolved from protecting civilians and surveying cease-fires to encouraging and assisting dialogue, overseeing elections and promoting human rights, a mission not without consequence.
121 men and women lost their lives during peacekeeping missions in 2009, and by May 28th 2010, that number had reached nearly 220. (source).
To see a comprehensive list of other commemorative days celebrated around the world, you can visit the French website journée-mondial.com (in French only). To date they have collected 246 days from various sources, including the United Nations, non-governmental organizations, religious institutions and other groups.
According to journée-mondial.com, there's no commemorative day yet attributed to May 30th, but if you wait for the 31st you can celebrate World Tobacco-Free Day.