The Mi'kmaq Indians that live in Nova Scotia and other parts of Canada have a very interesting and efficient calendar. It has 13 months of 28 days each. Each week has 7 days, and each month has 4 weeks. Since 13 x 28 = 364, there's an extra day added to the end of the year to make 365. This is designated as a holiday, the Year End Day. Every 4 years, a Leap Day is added, after the Year End Day. The year begins on the Vernal Equinox (March 20 or March 21). Many calendar reformists believe this to be the simplest and most sensible calendar ever devised.
The 13 months are named: Kjikús (Great Moon), Siwkewikús (Maple Sugar), Penamuikús (Birds Lay Eggs), Etquljuikús (Frogs Croaking), Nipnikús (Leaves Full Blossom), Peskewikús (Birds Shed Feathers), Kisikwekewikús (Ripening Time), Wikumkewikús (Moose Calling Time), Wikewikús (Fat Tame Animals), Keptekewikús (Rivers About To Freeze), Kiskewikús (Chief Moon), Punamujuikús (Spawn of Tom-Cod), and Apunknajit (Sun Is Very Strong).
The 7 days of the week are: Ekntiéwimk, Amskwesewey, Tápuewey, Sístewey, Néwewey, Kweltamultimk and Kespitek.
Source: http://www.mikmaq.com/calendars/