Cashflow and TimeValue Question

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• Subject: [mg131355] Cashflow and TimeValue Question
• From: Dana DeLouis <dana01 at icloud.com>
• Date: Mon, 1 Jul 2013 05:47:38 -0400 (EDT)
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```Hello.   When doing Net-Present value types of problems, I seem to
occasionaly get slightly different answers when compared to a very
365 day year, yet I don't see anything in the Mathematica documentation
on this.
I've reduced the issue down to these two simple examples.

1.  3 simple daily cash flows in a row.
cf[[1,1,1]] is returning the start date, or time 0.
The days per year is a fraction, so I use Rationalize to return
the values used for easy viewing.

cf=Cashflow[{
{{2009,12,29},a},
{{2009,12,30},b},
{{2009,12,31},c}
}];

Rationalize[TimeValue[cf,r,cf[[1,1,1]]],0]

a + b/(r+1)^(1/365) + c/(r+1)^(2/365)

It appears the program uses 365 days/year also.  This example would most
likely match.
We just note that the year 2009 is not a leap year.

2.   However, If I change the year to 2007, which is also not a leap
year, it appears that the program is using a 366 day year.  These types
use a constant 365 day year.

cf=Cashflow[{
{{2007,12,29},a},
{{2007,12,30},b},
{{2007,12,31},c}
}];

Rationalize[TimeValue[cf,r,cf[[1,1,1]]],0]

a + b/(r+1)^(1/366) + c/(r+1)^(1/183)

Note:  it's using 366 day year...
{1,2}/366
{1/366,1/183}

Does anyone have any insight?  I'm not sure what the standard convention is.
I just note that both years are non leap years, yet different methods of calculations.
It appears to me that the random use of 366 is causing the slightly different answers.