I recently discovered something about the way the HP12C does present value calculations I was not aware of. I'm trying to figure out if changing the way it caluculates is an easy push of a button, only solved by converting the periods to monthly etc.. In any event I can't figure out why the HP 12C calculates it like it does as, to me, it doesn't seem like the way anyone would want the calculation done. I tried it on an HP 19B and it worked as I intended. Anwyay, here is the problem.

I was trying to get a PV for annual rental payments. The term was supposed to be 68 months, so I'd used 5.667 years (end of period payments). I input the info as follows $173,250 PMT, 5.667 n, 6 i, and got a PV of $701,710. I didn't double check this anywhere. I got a call back today saying, the period should be 6 years, so I ran the same calculation with 6 n and got $851,926. I knew somethign was off, but couldn't figure out what.

I played around and realized for every "n" from 5 to 5.99 the PV number got smaller. I then figured out what the HP 12C did for my inputs was to put a zero payment in for the first period, and then discount five, $173,250 payments 1.667, 2.667, 3.667 etc. years.

Is my calculator set-up wrong or is this really how the HP 12C does this calculation? If so, it makes no sense to me as I can't imagine anyone wanting it to run that calculation with those inputs. As I said, if I put the same inputs into a 12B I get something around $830,000 which is what, I would have expected the 12C to tell me as well.