Take any 3x3 set of nine squares from a calendar and create a magic square using those nine dates. Describe a simple method for creating such a magic square. Repeat for any 4x4 square.

Source: Original.

Solutions were received from Kirk Bresniker, Joseph DeVincentis, Howard Wachspress, and Bernie Erickson.

Here are two methods:

For any 3x3 set of squares,

1. "Rotate" the eight outer squares by one position.

2. Swap each side value across the center.

For example, the dates on the left become the square on the right:

2 3 4 9 10 11 16 17 18 |
9 18 3 4 10 16 17 2 11 |

For any 4x4 set of squares,

1. Leave the corners and center four alone.

2. Swap each side number with its diagonal opposite.

For example, the dates on the left become the square on the right:

2 3 4 5 9 10 11 12 16 17 18 19 23 24 25 26 |
2 25 24 5 19 10 11 16 12 17 18 9 23 4 3 26 |

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