Just push the button ...A Dozenal CalculatorWe′ve been asked for a calculator

And here is what it looks like, 
(NB: This is for Windows; there is no Mac version.)
The display shows the value of π in base twelve.
The display can show up to *12 digits (or 8 significant figures using scientific notation).
Note that "A" stands for "ten" and "B" for "eleven", so, for example, "a dozen and ten" is written "1A".
In addition to the normal keys for calculations (which can be accessed from the keyboard as well as by the mouse), and A and B for ten and eleven, we have:
Summary of key functions:
(note that letters may be caps or lowercase)
Function  Keyboard  Function  Keyboard  
Numbers  0  9, a and b  Log  L  
Fractionals  ; or .  Antilog  CtrlL  
Scientific notation  ^ or i  Sine  s  
Change sign (+/)  _ or w  Arcsine  Ctrls  
Equals  = or Enter  Cosine  c  
+  + or d  Arccos  Ctrlc  
Subtract    Tangent  t  
Multiply  * or x  Arctan  Ctrlt  
Divide  /  π  Ctrlp  
delete last input  backspace  e  Ctrle  
Clear all  Esc  open bracket  ( or k  
Memory clear  e  close bracket  ) or Ctrlk  
Memory recall  r  Switch number base  n  
Memory   m  Switch angle system  f  
Memory +  p  Switch hints on/off  h 
To copy or paste a value to or from the clipboard right click the mouse for popup menu over the display area.