Check this out!

This is an online exhibit from the Smithsonian chronicling how the Lakota Sioux kept a calendar through pictures. This shows the work of several different "count keepers" and explains how they were able to sync their work up with European calendars.

One of those events, The Year the Stars Fell, was also widely known to non-Lakota people. The Smithsonian scholar Garrick Mallery recognized it as the Leonid meteor storm of November 1833, and he used this event to correlate the Lakota winter counts with the Western calendar.

Think about trying to deal with trying to remember all the stuff that's happened, even just since your kids were born, without resorting to using the numbers of the years. Then imagine trying to keep track of the history of everyone in a population going back as long as anyone can remember. Pretty mind blowing...