In many Anishinaabe and Haudenosaunee teachings, a turtle's back holds a calendar: 13 large plates in the center for the 13 moons of a year, and 28 small plates around the edge for the days of a moon. The Maya, who live today in Mexico and Central America, count days with two calendars that turn together like gears: the 260-day count (Tzolk'in), which joins 13 numbers to 20 day names, and the 365-day count (Haab'), 18 months of 20 days and 5 more days. They line up again after 18,980 days, 52 years of 365 days, a cycle called the Calendar Round. Maya day keepers in Guatemala still keep the 260-day count. The Maya figures come from the Smithsonian National Museum of the American Indian's Living Maya Time.
Five pages of number patterns. Page 1 counts the plates on a turtle's shell and skip counts by 28 for 13 moons. Page 2 finds 13 × 28 = 364 with an area model, then six stories about moons and days. Page 3 has six pairs of gears: students list multiples to find when the marked teeth meet again. Page 4 marks two cycles on strips of days and solves four stories, one about the Maya 260-day count. Page 5 builds the Calendar Round from 260 and 365, step by step. The first problem on each page is a worked example.
On page 1, let students count the shell's plates in their own way and compare: 5 down the middle and 4 on each side make 13. On page 3, cut gears from card with the same numbers of teeth and turn them together to check the answers.
Look at this year's calendar together: count how many full 28-day moons fit in 365 days, and how many days are left over.
This pack supports the following Common Core State Standards for Mathematics:
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Number patterns from two calendars of the Americas: the 13 moons and 28 days that many Anishinaabe and Haudenosaunee teachings connect to a turtle's back, and the Maya 260-day and 365-day counts. Students skip count, multiply 13 × 28, and find when two cycles line up again with least common multiples, up to the 52-year Calendar Round.
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