april the 7th as World Health Day was instituted by the World Health Organization(WHO) in 1948...WHO is the directing and coordinating authority for health within the United Nations system....so u have ur answer there.
btw...their agenda this yr r...protect health from the deteriorating effects of climate change.....along with projects like preventing HIV/AIDS..reducing child mortality..combating malaria etc... :)
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Ye...because they do not have any other suitable date ...because all other date are reserved for mothers day , fathers day, teachers day, childrens day, aunty's day, uncles day, house maid's day, bagal waali aunty's day etc etc.
Ya United Nations have connection with these things. Because they do not have other works na. :))))))))))))) baite baite bore hojaayenge.