YEARFRAC test cases

[robert_weir@us.ibm.com]

I put together these test cases in an attempt to exercise every "path" in 
the definition of basis 0 and basis 1 in the current ODF 1.2 draft.

I picked dates that were easy to calculate by hand, based on 90-day and 
180-day intervals.  For each test case I calculated the value manually, 
from the definition in the standard. 

I used this in an exercise at the recent ODF Plugfest, arguing that the 
logic behind YEARFRAC is at the center of many of the other financial 
calculations.

I'd invite you to take a look at this sheet in your spreadsheet 
application and see if your results differ from what I'm suggesting the 
correct answer is. 

-Rob

yearfrac.ods