Abbreviated Calendar

Some calendars with 28 days or 21 days chopped out of each month.

Isn't it interesting that the last days of the month always end up on the same days of the week as the first days of the month?

If you are good at taking numbers modulo 7, these calendars are good enough.

The month of February sometimes entirely disappears.

28-day cuts:

Sun Mon Tue Wed Thu Fri Sat
===========================
       |1   2   3  |1  |1
 2008  |January    |Feb|Mar
       |29  30  31 |29 |29
---------------------------
2   3  |1   2  |1   2   3
March  |April  |May
30  31 |29  30 |29  30  31
---------------------------
1   2  |1   2   3  |1   2
June   |July       |August
29  30 |29  30  31 |29  30
---------------------------
3  |1   2  |1   2   3  |1
Aug|Septemb|October    |Nov
31 |29  30 |29  30  31 |29
---------------------------
2  |1   2   3
Nov|December
30 |29  30  31

Sun Mon Tue Wed Thu Fri Sat
===========================
               |1   2   3
 2009          |January
               |29  30  31
---------------------------
1   2   3  |1   2  |1   2
March      |April  |May
29  30  31 |29  30 |29  30
---------------------------
3  |1   2  |1   2   3  |1
May|June   |July       |Aug
31 |29  30 |29  30  31 |29
---------------------------
2   3  |1   2  |1   2   3
August |Septemb|October
30  31 |29 30  |29  30  31
---------------------------
1   2  |1   2   3
Novembe|December
29  30 |29  30  31

21-day cuts:

Sun Mon Tue Wed Thu Fri Sat
===========================
 2008  |January
       |1   2   3   4   5
---------------------------
January            |Februar
6   7   8   9   10 |1   2
---------------------------
February               |Mar
3   4   5   6   7   8  |1
---------------------------
March
2   3   4   5   6   7   8
---------------------------
March  |April
9   10 |1   2   3   4   5
---------------------------
April          |May
6   7   8   9  |1   2   3
---------------------------
May
4   5   6   7   8   9   10
---------------------------
June
1   2   3   4   5   6   7
---------------------------
June   |July
8   9  |1   2   3   4   5
---------------------------
July               |August
6   7   8   9   10 |1   2
---------------------------
August
3   4   5   6   7   8   9
---------------------------
Aug|September
10 |1   2   3   4   5   6
---------------------------
September  |October
7   8   9  |1   2   3   4
---------------------------
October                |Nov
5   6   7   8   9   10 |1
---------------------------
November
2   3   4   5   6   7   8
---------------------------
Nov|December 
9  |1   2   3   4   5   6
---------------------------
December
7   8   9   10

Sun Mon Tue Wed Thu Fri Sat
===========================
 2009          |January
               |1   2   3
---------------------------
January
4   5   6   7   8   9   10
---------------------------
February
1   2   3   4   5   6   7
---------------------------
March
1   2   3   4   5   6   7
---------------------------
March      |April
8   9   10 |1   2   3   4
---------------------------
April              |May
5   6   7   8   9  |1   2
---------------------------
May
3   4   5   6   7   8   9
---------------------------
May|June
10 |1   2   3   4   5   6
---------------------------
June       |July
7   8   9  |1   2   3   4
---------------------------
July                   |Aug
5   6   7   8   9   10 |1
---------------------------
August
2   3   4   5   6   7   8
---------------------------
August |September
9   10 |1   2   3   4   5
---------------------------
September      |October
6   7   8   9  |1   2   3
---------------------------
October
4   5   6   7   8   9   10
---------------------------
November
1   2   3   4   5   6   7
---------------------------
Novembe|December
8   9  |1   2   3   4   5
---------------------------
December
6   7   8   9   10