Yes, there is such an observance as Blasphemy Day and it is celebrated on this day each year.
Blasphemy Day was founded in 2009 and September 30th was the day chosen for observance, “to coincide with the anniversary of the publication of satirical drawings of the Muslim prophet Muhammad in one of Denmark’s newspapers, resulting in the Jyllands-Posten Muhammad cartoons controversy.”
According to Ronald A. Lindsay, president and CEO of the Center for Inquiry, a society is not truly free unless people can freely air their views on any subject — including God.
So, if you haven’t already done so, get your blasphemy on before the day is over, $@#^%!