05-10-2017, 01:28 PM

I have been in seach of simple algorithm to calculate dDays between two dates.

The JDN method is too heavy to my use (DM15/HP15C) as it needs to be accurate only between about 100 year time window.

I did found one that suits my use at: https://groups.google.com/forum/#!topic/...c9rcvY7d2s

Now interesting enough I did put 3 different methods to the excel worksheet to compare them simultaneusly.. If I take DDays from 28.2.1900 and 28.2.2100 I get results:

Excel (365): 73050

JDN-JDN^^: 73049

HP50g DDAYS: 73049

SIMPLE DDAYS**: 73050

WAlpha: 73049 ( https://www.wolframalpha.com/input/?i=DA...+28.2.2100 ) PS. As late though

So which ones are correct? :/ Any idea.. I trush 50g more than excel, since also the JDN-JDN gives the same result but..

First I though that excel handles days as Ddays+1, but no it were false assumption since

DDAYS(28.3.1900,28.2.2100) returns as follows:

Excel: 73021

JDN-JDN: 73021

HP50g DDAYS: 73021

Simple DDAYS: 73020

EDIT2: Ahaa, Excel DAYS function starts at year 1900 that might explain this difference in this particular case.

Interesting.. Back to jellyfying my brains with day algorithms. :Z

** From mailinglist discussion

Y <- start year

M <- start month

D <- start day

Y <- Y-1

M <- M+13

X <- int(365.25*Y)+int(30.6*M)+D

https://groups.google.com/forum/#!topic/...c9rcvY7d2s

^^

As given in wikipedia.org

https://en.wikipedia.org/wiki/Julian_day

https://wikimedia.org/api/rest_v1/media/...0958a53d61

The JDN method is too heavy to my use (DM15/HP15C) as it needs to be accurate only between about 100 year time window.

I did found one that suits my use at: https://groups.google.com/forum/#!topic/...c9rcvY7d2s

Now interesting enough I did put 3 different methods to the excel worksheet to compare them simultaneusly.. If I take DDays from 28.2.1900 and 28.2.2100 I get results:

Excel (365): 73050

JDN-JDN^^: 73049

HP50g DDAYS: 73049

SIMPLE DDAYS**: 73050

WAlpha: 73049 ( https://www.wolframalpha.com/input/?i=DA...+28.2.2100 ) PS. As late though

So which ones are correct? :/ Any idea.. I trush 50g more than excel, since also the JDN-JDN gives the same result but..

First I though that excel handles days as Ddays+1, but no it were false assumption since

DDAYS(28.3.1900,28.2.2100) returns as follows:

Excel: 73021

JDN-JDN: 73021

HP50g DDAYS: 73021

Simple DDAYS: 73020

EDIT2: Ahaa, Excel DAYS function starts at year 1900 that might explain this difference in this particular case.

Interesting.. Back to jellyfying my brains with day algorithms. :Z

** From mailinglist discussion

Y <- start year

M <- start month

D <- start day

Y <- Y-1

M <- M+13

X <- int(365.25*Y)+int(30.6*M)+D

https://groups.google.com/forum/#!topic/...c9rcvY7d2s

^^

As given in wikipedia.org

https://en.wikipedia.org/wiki/Julian_day

https://wikimedia.org/api/rest_v1/media/...0958a53d61