Doomsday
As we all know, you need a different calendar for every year.
This is because for a ‘normal’ calendar the first day of the week
is Sunday. In other words: if you keep the first day of the week constant,
then the calendar changes from year to year.
But it is also possible to keep the calendar constant,
if you are willing to accept a different first day of the week for every year!
This day is called Doomsday.
That means that in the calendar below,
the first column of every month is Doomsday.
For 2009, Doomsday is Saturday.
For every month, one easy to remember Doomsday is shown in red.
These are: 4/4, 6/6, 8/8, 10/10, 12/12, the two couples 9/5, 5/9
and 7/11, 11/7, January 3, February 0, and March 0.
The two months on the left (January and February) apply only to leap years.
For those two months, Doomsday is shifted by one day.
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January
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| 27
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| 31
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January
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| 1
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| 4
| 5
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| 7
| 8
| 9
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| 11
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| | 31
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April
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| 24
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| 26
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| 30
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July
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| 1
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| 31
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October
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| 1
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February
| 1
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| 4
| 5
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| 9
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February
| 0
| 1
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| 3
| 4
| 5
| 6
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| 8
| 9
| 10
| 11
| 12
| 13
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| 15
| 16
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| 20
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| 22
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| 24
| 25
| 26
| 27
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May
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| 1
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| 10
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| 31
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August
| 1
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| 31
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November
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| 1
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| 4
| 5
| 6
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| 8
| 9
| 10
| 11
| 12
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| 26
| 27
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| 30
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March
| 0
| 1
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| 4
| 5
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| 8
| 9
| 10
| 11
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| 31
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June
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September
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| 30
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December
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| 1
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| 31
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