A Calendar Math Project

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Students factor 365 in an attempt to create a better system of months and weeks than our current calendar.

This video is a simplified version of the Create A Civilization: Calendars video.


  1. Students are asked (by the Supreme Council for Calendars) to clear up the confusing mess of 28, 30, and 31-day months by factoring 365.

  2. Students will discover that 365 has very few factors: 1, 5, 73, and 365 -- not so great for even months. We introduce intercalary days: days outside of any month. Students reserve a few days for a special holiday, then create nice, even months.

  3. Now students will divide those months into even weeks so that the year and each month have nice, whole numbers of weeks.

  4. Finally, we do some naming: what will we call our months? What about our days of the week?


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Related CCSS Math Standards

3.OA.1, 3.OA.2, 4.OA.4