Date -> Day of week conversion
Ijaz Rashid Malik
Could someone please forward me algorithm to convert the date (in dd.mm.yy
or yy.mm.dd format, but assume individual fields can be obtained as integers)
to corresponding day of the week.
Thanks very much.
Malik
Tomohiko Sakamoto
umm...@ccu.umanitoba.ca (Ijaz Rashid Malik) says:
>
> Could someone please forward me algorithm to convert the date (in dd.mm.yy
> or yy.mm.dd format, but assume individual fields can be obtained as integers)
> to corresponding day of the week.
Please try this:
/*
* 1 <= m <= 12, y > 1752 (in the U.K.)
*/
dayofweek(y, m, d)
{
y -= m < 3;
return (y + y/4 - y/100 + y/400 + "-bed=pen+mad."[m] + d) % 7;
}
--
T. Sakamoto
Janos A. Haide
Since you have crossposted in comp.lang.c I'd say that you can simply
initialize a few fields on a struct tm and then apply mktime() on it.
One of the fields will be set to the week of day.
As far as a generic formula goes, here is one I've seen a few days ago
(PASCAL-ish):
N:=(Trunc(M*2.6-0.1)+D+Y+Y div 4+5*C+C div 4) mod 7
Where:
D = day of month
Y = year of the century.
C = century.
M = Month - 2.
( January M=11 , February M=12 )
Result is an 0-6 integer.
Later,
Janos
jha...@novell.com
der Mouse
> In article <Bz3I8...@ccu.umanitoba.ca>, umm...@ccu.umanitoba.ca (Ijaz Rashid Malik) says:
>> Could someone please forward me algorithm to convert the date
> Please try this:
[...]
> return (y + y/4 - y/100 + y/400 + "-bed=pen+mad."[m] + d) % 7;
You would be much better off writing "\3\0\3\2\5\0\3\5\1\4\6\2\4"
instead of "-bed=pen+mad."; that way you aren't dependent on ASCII. (I
assume ASCII is what it's intended to be used with; I didn't go testing
it.) For example, converting that string to EBCDIC, I find that it's
equivalent to "\5\4\0\6\0\4\0\2\1\1\3\6\5" then....
der Mouse
