Zeller’s congruence

Zeller’s congruence is an algorithm devised by Christian Zeller to calculate the day of the week for any Julian or Gregorian calendar date.  Basically, SpeedCalendar requires mental arithmetic to calculate the day of the week.  There are several technique to do it.


  1. Pure calculation
  2. Finger method
  3. x1.25 method
  4. Quotient method
  5. 28/56/84 method
  6. Kurukuru method
  7. Rote memorization method

The summary material (document or youtube) will be disclosed one by one.  For the time being, please contact us for Special Lesson below.

Youtube manual

Japanese version.

【カレンダー】曜日計算方法! 任意の日付の曜日を当てられるようになりたい方へ!(日本語、ツェラーの公式)

Chinese version

微博 bilibili 优酷 爱奇艺 Youtube

English version

Coming soon..

Special Lesson

These methods can be introduced to you over the Internet (e.g. Zoom, Skype, Teams), as far as the Speed Calendar Commissioner is available.

  • Free of charge (treat beer is welcome!)
  • English, Chinese and Japanese are acceptable.
  • Consideration of time difference is required, commissioner lives in Japan.

Useful Information

Quick Note

L2DV table

2021 Table for quick calculation