March 14th was Pi day. Not the day we eat lots of pie but a day to celebrate the ratio of the circumference to the diameter of a circle; namely Pi. Why is today Pi day? Because Pi is 3.14(and an infinite load more digits) and March 14th is 3/14 in the American system of date formatting.
Year 6 conducted an investigation to find this special ratio by measuring, and comparing mathematically, the circumference and diameter of a range of circular objects.