(15C) Julian Day to Day of Week [ISO; 12C Formula]

[Dieter]

(08-26-2016 01:39 PM)Nick Wrote:  Formula: ISO Day of Week = JD MOD 7 + 1
(...)
Comments:

14 INT(x + .5) ' Rounding per precision loss during MOD

Yes, using FRAC for the mod function will produce roundoff errors.
But why don't you simply do it this way?

Code:

01 GSB 0
02 ENTER
03 ENTER
04 7
05 /
06 INT
07 7
08 *
09 -
10 1
11 +
12 RTN

That's shorter and does not require any rounding.
BTW, I assume the first step is not LBL 0 but GSB 0 (to call the JDN routine). ;-)

While we're at it: may I link to my HP35s calendar programs?
They convert from and to JDN, calculate the day of week and implement a ΔDAYS and DATE+ function and more.

Dieter