Calculating day-of-week in years greater than 9999

I was wondering if there are any algorithms that calculate the day of week in years that are g开发者_高级运维reater than the year 9999.

Algorithms such Zeller’s algorithm or this one here gives false results, since they handle only 4 digit year.

Thank you.

You don't actually need a new algorithm. As long as you have one algorithm with a range of 400 years (or more), you can bring any date inside the range of that algorithm. This works because the Gregorian calendar repeats every 400 years (XX/YY/ZZZZ is the same weekday as XX/YY/(ZZZZ+400)).

So, if we assume that you have some algorithm that works for the dates 1/1/1600 to 31/12/1999 (both inclusive), you can calculate the weekday for any date by using (year mod 400)+1600 as the year.

If you don't have a 400-year range starting on 1/1/XXXX (where XXXX mod 400 = 0), you need to manipulate the date slightly different to get the right result (instead of adding 1600 to the year, add X*400, where X is an integer such that some of the dates will be in the range, then add or subtract 400 to the year for those dates that are outside of the range).

http://lxr.linux.no/linux/net/netfilter/xt_time.c for example simply counts it out. To reduce the number of iterations in loops, static tables may be used, as has been done there.