The Dozenal Society of Great Britain seeks to replace the base 10 number system with one based on base 12.

Dozenalists claim that this would ease mental math, especially with fractions and multiplication. For example, in dozenal math, 1/3 is 0.4, and the multiplication table shows more regularities and is therefore easier to memorize.

Dozenal requires two additional digits, and the society suggests the use of an upside-down 2 and 3.

Their website: http://www.dsgb.orbix.co.uk