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April (North America: Wednesday of last full week) - Administrative Professionals' Day
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April 1 - April Fools' Day
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April 1 - Edible Book Festival
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April 10 - Siblings Day (some countries)
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April 10 - World Homeopathy Day
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April 11 - International Louie Louie Day
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April 12 - Cosmonautics Day
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April 12 - Equal Pay Day
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April 13 - FND Awareness Day
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April 14 - Black Day (South Korea)
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April 14 - Cake and Cunnilingus Day
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April 15 - Day of Dialogue
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April 15 - World Bleeding Disorders Awareness Day
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April 16 - Foursquare Day
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April 16 - National Healthcare Decisions Day (US)
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April 16 - World Voice Day
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April 17 - World Haemophilia Day
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April 17, 18 and 19 have been used - Record Store Day
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April 18 - International Day For Monuments and Sites
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April 19 - Bicycle Day
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April 2 - International Children's Book Day
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April 2 - World Autism Awareness Day
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April 20 - Global cannabis culture
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April 21 - Day of Silence
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April 21 - National Tea Day
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April 22 - Earth Day
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April 22 - International Mother Earth Day
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April 22 (UK) - Administrative Professionals' Day
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April 23 - English Language Day
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April 23 - World Book and Copyright Day
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April 24 - Armenian Genocide Remembrance Day
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April 24 - Fashion Revolution Day
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April 24 - World Day for Laboratory Animals
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April 24 - World Meningitis Day
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April 25 - ANZAC Day
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April 25 - DNA day
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April 25 - International Delegate's Day
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April 25 - Liberation Day (Italy)
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April 25 - Parental Alienation Awareness Day
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April 25 - World Malaria Day
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April 27 - Freedom Day (South Africa)
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April 27 - King's Day (The Netherlands)
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April 28 - World Day for Safety and Health at Work
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April 29 - Day of Remembrance for all Victims of Chemical Warfare
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April 4 - International Day for Mine Awareness and Assistance in Mine Action
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April 5 - National Maritime Day
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April 6 - International Day of Sport for Development and Peace
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April 6 - World Bohring-Opitz Syndrome Awareness Day
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April 7 - World Health Day