When is Oklahoma Day in United States?

April 1, April Fool's Day April 2, World Autism Awareness Day April 2, Pascua Florida Day April 4, United Nations' Mine Awareness Day April 6, National Tartan Day April 6, International Day of Sport for Development and Peace April 7, United Nations' World Health Day April 7, Day of Remembrance of the Victims of the Rwanda Genocide April 8, National Library Workers' Day April 12, International Day of Human Space Flight April 13, Passover (first day) April 13, Thomas Jefferson's Birthday April 13, Palm Sunday April 15, Tax Day April 15, Father Damien Day April 16, Emancipation Day April 17, Maundy Thursday April 18, Orthodox Good Friday April 18, Good Friday April 18, International Day for Monuments and Sites April 19, Holy Saturday April 19, Orthodox Holy Saturday April 20, Orthodox Easter April 20, Last Day of Passover April 20, Easter Sunday April 20, Chinese Language Day April 21, Orthodox Easter Monday April 21, San Jacinto Day April 21, Patriot's Day April 21, Boston Marathon April 21, Easter Monday April 22, Earth Day April 22, Oklahoma Day April 23, World Book and Copyright Day April 23, Yom HaShoah April 23, Administrative Professionals Day April 23, English Language Day April 24, Take our Daughters and Sons to Work Day April 25, Arbor Day April 25, World Malaria Day April 26, Confederate Heroes' Day April 26, World Intellectual Property Day April 26, International Chernobyl Disaster Remembrance Day April 28, Confederate Memorial Day April 28, World Day for Safety and Health at Work April 28, State Holiday April 29, Day of Remembrance for all Victims of Chemical Warfare April 30, International Jazz Day