Try this example taken from Hp Journal (oct. 77) :
n=111.1111111
i=2.222222222
PV=333.3333333
PMT=4.444444444
and solve for FV
Results
HP92 : -5931.82294 (source HP Journal)
HP37E : -5931.82294
HP38E/C : -5931.82294
HP12C : -5926.306294 ???
HP10B : -5931.82294
HP17BII : -5931.82294
HP10B : -5931.82294
HP48G : -5931.82294
All but the 12C give the correct mathematical result (-5931.82294) but only the 12C gives the correct financial result(-5926.306294). In case of noninteger n, the 12c use the fractional part as a odd first period (cf hp 12c user's manual pp.50-51). With others calculators you'll have to do it yourselve (cf hp17BII owner's manual p.160).
Does anyone knows why the 12c is the only calculating with odd period ?