Because one turn is 2 π π radians, some have proposed representing 2 π π with a single letter. In 2010, Michael Hartl proposed using the Greek letter τ τ (tau), equal to 2 π π and corresponding to one turn, for greater conceptual simplicity when stating angles in radians. This proposal did not initially gain widespread acceptance in the mathematical community, but the constant has become more widespread, having been added to several major programming languages and calculators.