June 14th is World Blood Donor day, first established in 2005 to recognize those who volunteer for the altruistic procedure (not precedure) of donating blood. The day is held on the birthday of Karl Landsteiner, who won the Nobel Prize in Medicine for creating the ABO system of blood groups.
Landsteiner likely didn’t predict the interesting superstitions that have grown up around blood types. In Japan, blood types are linked to personalities: for example, those with type O are considered to be optimistic, sociable, and stubborn.
Of course, like with astrological star signs, the blood type personalities vary depending on who you ask. Other interesting myths about blood type have developed around the world, including the (unproven) notion that those with type A are more prone to hangovers.
(Image of red blood cells from Britannica Online Encyclopedia)