| Month | Subject | Author | Remark | |
| 04-01 | Why is the XII vertical? |
Hans de Rijk | ||
| 04-02 | The bigger, the better? | Hans de Rijk | About the dimensions of an analemmatic sundial |
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| 04-03 | The shadow moves back | Fer de Vries | About the retrogradation | |
| 04-04 | Reusing the pattern | Fer de Vries | ||
| 04-05 | Poem | Leo Theunissen | ||
| 04-06 | Horizontal sundial design graph |
Fer de Vries | Regiomontanus 1474 | |
| 04-07 | Equal is unequal | Fer de Vries | Suntime hour isn't always 60 minutes |
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| 04-08 | Islamic prayer lines | Fer de Vries | Zuhr, Asr-i evvel, Asr-i sāni | |
| 04-09 | The 1988 poster | Fer de Vries | Tenth anniversary De Zonnewijzerkring | |
| 04-10 | A clock for an indicator | Fer de Vries | Sundial by Bill Newman of Australia |
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| 04-11 | Dialling scales | Fer de Vries | ||
| 04-12 | Babylonian en Italic hours | Fer de Vries | Part 1 | |