The Human Calculator Calendar was developed by Scott Flansburg who is known as the Human Calculator. It is a solar 13-month calendar of 4-week months with the extra day being the first day, or rather the zeroth day of the year and belonging to the first month but to no week. The leap rules are unclear at this point. The months are named by cardinal numbers starting at zero.
| Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|
| 00 | ||||||
| 01 | 02 | 03 | 04 | 05 | 06 | 07 |
| 08 | 09 | 10 | 11 | 12 | 13 | 14 |
| 15 | 16 | 17 | 18 | 19 | 20 | 21 |
| 22 | 23 | 24 | 25 | 26 | 27 | 28 |
| Mon | Tue | Wed | Thu | Fri | Sat | Sun |
|---|---|---|---|---|---|---|
| 01 | 02 | 03 | 04 | 05 | 06 | 07 |
| 08 | 09 | 10 | 11 | 12 | 13 | 14 |
| 15 | 16 | 17 | 18 | 19 | 20 | 21 |
| 22 | 23 | 24 | 25 | 26 | 27 | 28 |
Sometimes it’s said to start the week on Monday[1], in other documents it starts Sunday[2]. Perhaps it’s just whatever happens to be the DOW of 2 January in the Gregorian calendar, since 1 January is special Day Zero in the Human Calculator Calendar, as indicated on the frontpage of the 2020 edition saying: “This calendar works best when January 1st is a Sunday. The next time that occurs is 2023.”[3]