July 22nd:
July 22nd (international numeric date is 22/7/year) is Pi Approximation Day and celebrates the discovery of the calculation of the Math Symbol Pi – which is approximately calculated at 22/7 (22 divided by 7).
Peter Kevin Connell from Today in Heritage History warns:
“Please be courteous driving today and try to avoid all the International Mathematician Parades. Most mathematician marchers generally have problems negotiating traffic while dressed in Rhombus and Trapezoid costumes.”
May 14th:
May 14th is what is typically known as Pi Day, and is an unofficial holiday commemorating the mathematical constant p (pi). Pi Day is celebrated on March 14 (or 3/14 in month/day date format), since 3, 1 and 4 are the three most significant digits of p in the decimal form. In 2009, the United States House of Representatives supported the designation of Pi Day.
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What is Pi?
The simplest visualization of Pi is probably a circle.
Half the circumference of a circle with radius 1 is exactly Pi!
The area inside that circle is also exactly Pi!
Fun Pi Images
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References:
Wikipedia: Pi Day
Freaking News Photoshop Contests: Pi Day pictures
Today in Heritage History ~ Where History Meets Humor: July 22, 2010- BB&B and Pi
Motley News & Politics 
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