How to Calculate the Day of the Week from Any Date

I am trying to learn how to calculate date from any century. I am aware of these codes but what are the codes for a century like 1600 or 2400? Is there a formula? Is there a pattern? If so is it 42064204206420… or 420642064206? This is what I know…

  • 1700s = 4
  • 1800s = 2
  • 1900s = 0
  • 2000s = 6
  • 2100s = 4
  • 2200s = 2
  • 2300s = 0.
    Any help is appreciated.
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What method is this for? It reminds me of the century anchors for the Doomsday algorithm, but the numbers are different.

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Shameless self promotion…

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… I would say the pattern is obvious, and can be proved by :date: … The reason why you can’t see it might because you didn’t read the calendar?
Put it simple, those years u stated please focus on 1 Jan, xxxx and u will know what is the number for 1600, 2400 and so on.

Forgive me, bing a bit rude. Memorisation and techniques are handful, but observation :eye: is another :key:, it can greatly trim the memory capacity of provable objects. :upside_down_face:

By the way, I found this forum is shifting to a IQ or fun :speech_balloon: channel, On the one hand, the memory side is dimmer, on the other hand, it’s a diversified brainner food court. (・・?)

He posted it in the mental math subsection, so all good in my opinion.

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My code is different but according to the code you mentioned.

2400 => 6
1600 => 6

1200 => 6
1300 => 4
1400 => 2
1500 => 0

1600 => 6
1700 => 4
1800 => 2
1900 => 0

2000 => 6
2100 => 4
2200 => 2
2300 => 0

2400 => 6
2500 => 4
2600 => 2
2700 => 0

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The codes for the centuries repeat every 4 centuries, because in 400 years there is an integer number of weeks: 146097 days is exactly 20871 weeks.

In case it is relevant, here is an explanation of how to calculate calendar dates, but using 0 as the code for 2000s and 0 for Feb/Mar/Nov, which is the way to get as many zeros as possible into the method: https://worldmentalcalculation.com/how-to-calculate-calendar-dates/

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