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September 1 - National Insurance Day (Sri Lanka)[168]
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September 1 - Random Acts of Kindness Day (New Zealand)
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September 10 - World Suicide Prevention Day
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September 11 - Patriot Day
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September 12 - ATSEP Day
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September 13 - Depression awareness and suicide prevention (Australia)
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September 13 - International Chocolate Day, Birthday of Milton S. Hershey
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September 14 - Hindi Day
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September 14 - National Quiet Day (UK)
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September 15 - Engineer's Day (India)
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September 15 - International Day of Democracy
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September 16 - International Day for the Preservation of the Ozone Layer
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September 16 - Malaysia Day
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September 16 - Start of Mexican Independence Day
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September 17 - World Patient Safety Day
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September 18 - World Water Monitoring Day
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September 19 - International Talk Like a Pirate Day
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September 2 - Victory over Japan Day (US)
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September 20 - International Day of University Sport
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September 21 - International Day of Peace
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September 22 - World Car Free Day
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September 22 - World Rhino Day
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September 23 - Celebrate Bisexuality Day
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September 23 - International Day of Sign Languages
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September 24 - Heritage Day (South Africa)
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September 25 - As You Wish Day
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September 25 - World Pharmacists Day
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September 26 - European Day of Languages
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September 26 - World Contraception Day
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September 27 - World Tourism Day
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September 28 - Ask a Stupid Question Day
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September 28 - International Right to Know Day
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September 28 - International Safe Abortion Day
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September 29 - World Heart Day
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September 3 - Skyscraper Day
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September 30 - Botswana Day
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September 30 - International Translation Day
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September 4 - National Finnish Food Day (Finland)
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September 5 - International Day of Charity
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September 6 - Colour Blindness Awareness Day
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September 6 - Defense Day (Pakistan)
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September 7 - Brazilian Independence Day
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September 7 - International Day of Clean Air for Blue Skies
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September 8 - International Literacy Day
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September 8 - World Physical Therapy Day
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September 9 - International Day to Protect Education from Attack
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September 9 - International Fetal Alcohol Spectrum Disorder (FASD) Awareness Day