Slight problem with day of the week calculation (base doomsday for a century)

From this online calculator: http://homer.freeshell.org/dd.cgi using its data I've successfully written a working version, however its data is limited to years 1500 to 2600. I want to modify (and make a better one) so that I can calculate for any year > 2600.

Referri开发者_如何学Gong to Table X, is there actually a formula to calculate the base doomsday for all base centuries (above 2600)?

I've tried working it out myself by putting centuries higher than this e.g. 2700 gave me a base doomsday of '00', 2800 gave '02;, 2900 back to '00' again...

Help appreciated.

As I understand it, that page's “Base Doomsday” is just an offset to allow for the four-hundred-year cycle of leap day calculations. So, you can extend it indefinitely into the future simply by adding blocks of four centuries.

Are there any other calculators out there that do this?

Two common methods for calculating the day of the week given a date are Doomsday, which you are using, and Zeller's Congruence

www.merlyn.demon.co.uk provides some really interesting information on date/time calculations, various calendar systems and significant dates as they relate to calendar/date calculations.

The calculator at this link http://homer.freeshell.org/dd.cgi is the best in terms of explaining doomsday algorithm cleanly and clearly for human, with one little caveat.

If you input 2/29/1900, it would say it's a Thursday. Well, there is no 2/29/1900, because it's not a leap year.

Of course if your input 1/35/2016, it would "garbage-in-garbage-out" for you as well.

Imagine there are only 364 days in a year, then the day of week for each date will never change year after year, because mod(364,7)==0.

But we have 365 days a year, so the day steps forward 1 each year, that's where the second term mod(year, 7) comes from.

In addition, every 4 year, there is a leap year, which contributes to the last term mod(year, 4).

But every 100 years, you subtract a leap year, and every 400 years, you add one leap year. That's where the first term "3,2,0,5" comes in.

You see, it's all because of this leap year, and mod(365,7)==1 business.

7/11, 5to9 helps to remember table Z greatly.