Calendar Wiki

The Quepennura Leap Week Calendar builds upon the Gregorian Calendar, but has a distinct irregular month layout and an unusual leap cycle.


  • Regular months (01, 03–06, 08–11) have 31 days each.
  • February (02) and July (07) have only 30 days each.
  • December (12) has 25 days in a common year and 32 days in a leap-week year.

Since only the last month of the year has a variable length, all months start on a fixed day of the week (and none of them on Wednesday or Sunday):

  1. January starts on a Monday to align with international standard ISO 8601.
  2. February starts on a Thursday.
  3. March starts on a Saturday to align with alleged Roman or Christian traditions of the Julian calendar.
  4. April starts on a Tuesday.
  5. May starts on a Friday.
  6. June starts on a Monday.
  7. July starts on a Thursday.
  8. August starts on a Saturday.
  9. September starts on a Tuesday.
  10. October starts on a Friday.
  11. November starts on a Monday.
  12. December starts on a Thursday.

For the number of weeks per months, the Thursday rule is explicitly applied, which leads to an irregular pattern:

  1. January: 4 weeks
  2. February: 5 weeks
  3. March: 4 weeks
  4. April: 5 weeks
  5. May: 4 weeks
  6. June: 4 weeks
  7. July: 5 weeks
  8. August: 4 weeks
  9. September: 5 weeks
  10. October: 4 weeks
  11. November: 4 weeks
  12. December: 4/5 weeks

Fiscal quarters[]

In common years of 364 days, the *weeks* of three consecutive months are counted as a quarter-year, but in leap years of 371 days, the *days* of three consecutive months are counted as a quarter-year. This can be done in one of the following three ways, the first of which is preferred:

  1. (A) Starting with March: 13:13:13:13 weeks or 93:92:93:93 days.
  2. (B) Starting with January: 13:13:14:12 weeks or 92:93:92:94 days, so week 5 of September should be week 0 of October in common years and 1 October should be 32 September in leap years.
  3. (C) Starting with February: 13:13:12:14 weeks or 92:93:94:92 days, so week 1 of February should be counted as week 5 of January in common years and 31 January should be counted as 0 February in leap years.

Leap cycle[]

The leap cycle repeats every 479 years or 24,993 weeks. It has 85 leap weeks in it, spread uniformly. The mean length of a year is therefore 365.24217119 days.

External links[]