The Tesserods Calendar shares some aspects of the Butterfly Calendar, which it can be considered an alternative to. Like Butterfly, a full seven-day week only occupies six dates with Saturday and Sunday combined.

The year follows a pattern of a regular three-month period followed by a long month. I call that pattern a tesserod, from Greek "tessera": four. It gives its name to the calendar.

Regular months have 25 dates. The long months are April and August with 5 weeks or 30 dates, and December with 28 dates.

## Leap years

On a leap year December has 30 dates like other long months. A cycle begins with three leap years followed by ninety regular years. The next leap cycle will start on Thursday 28 December 2045 (Tess: 1 January 2046).

The average year length is:

${\displaystyle {\frac {7}{6}}\times {\frac {93\times (9\times 25+2\times 30)+90\times 28+3\times 30}{93}}=365.24194}$

## Sample tesserod

Sample: Days in the four months of a tesserod
Month 1 Month 2 Month 3 Month 4
M T W T F SS M T W T F SS M T W T F SS M T W T F SS
1 2 3 1 2 1 1 2 3 4 5 6
4 5 6 7 8 9 3 4 5 6 7 8 2 3 4 5 6 7 8 9 10 11 12 13
10 11 12 13 14 15 9 10 11 12 13 14 8 9 10 11 12 13 13 14 15 16 17 18
16 17 18 19 20 21 15 16 17 18 19 20 14 15 16 17 18 19 19 20 21 22 23 24
22 23 24 25 21 22 23 24 25 20 21 22 23 24 25 25 26 27 28 29 30