HP Prime: Day Number of the Year
01-21-2014, 03:31 PM (This post was last modified: 01-21-2014 09:21 PM by Damien.)
Post: #2
 Damien Junior Member Posts: 29 Joined: Dec 2013
RE: HP Prime: Day Number of the Year
Hi everyone,

For any gregorian date (year>1582). The Nth day of the year can be calculated with the formulas:

For non leap year:
N=INT(275*Month/9)-2*INT((Month+9)/12)+Day-30
For leap year:
N=INT(275*Month/9)-INT((Month+9)/12)+Day-30
With Month from 1 to 12, Day from 1 to 31.
(Taken from a book about astronomical calculation written by Jean MEEUS)

For the Prime something like that should work fine:
Code:
 EXPORT Date2Days(date) BEGIN LOCAL b,a,m,j; // date : [YYYY].[MM][DD]  IP(date)▶a; // YYYY  IP(FP(date)*100)▶m; // MM  IP(FP(FP(date)*100)*100)▶j; // DD // gregorian leap year ?  IF (NOT(a MOD 4) AND a MOD 100)        OR (NOT (a MOD 400)) THEN    b:=1; // leap year   ELSE   b:=2; //ordinary year  END;  RETURN IP(275*m/9)-b*IP((m+9)/12)+j-30; END;

Enter dates in HP Prime format : YYYY.MMDD

Example: 1970 june 9th (1970.0609) gives N=160.

Regards,

Damien.
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 Messages In This Thread HP Prime: Day Number of the Year - Eddie W. Shore - 01-21-2014, 01:24 PM RE: HP Prime: Day Number of the Year - Damien - 01-21-2014 03:31 PM

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