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+--- Thread: (15C) Julian Day to Day of Week [ISO; 12C Formula] (/thread-6731.html)
(15C) Julian Day to Day of Week [ISO; 12C Formula] - Nick - 08-26-2016 01:39 PM
Formula: ISO Day of Week = JD MOD 7 + 1
- Same formula as 12C [1 = Monday .. 7 = Sunday]
Input: X = JD (Julian Day)
Output: X = DOW (ISO Day of Week)
Size: 15 Bytes
Requires: (15C) MM.DDYYYY or DD.MMYYYY to Julian Day [Stack-Only] (or equivalent)
Note: The stack is not preserved.
Enjoy,
Nick
Code:
01 LBL 0
02 ENTER
03 ENTER
04 7
05 /
06 LSTx
07 X<->Y
08 FRAC
09 *
10 1
11 .
12 5
13 +
14 INT
15 RTNComments:
14 INT(x + .5) ' Rounding per precision loss during MOD
RE: (15C) Julian Day to Day of Week [ISO; 12C Formula] - Dieter - 09-18-2016 05:39 PM
(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 RTNThat'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