As we've gathered from the closing lines of all three Louisiana Purchase documents, the original documents were written in French, and both French and English copies were signed into officialdom.

But even though the documents were translated and copied from French into English, there are a few little details that just didn't translate. And for those guys, a special dispensation was made: they appear in French and English in both documents.

We're talking, of course, about the dates.

Dates?! Doesn't everyone use the same calendar?

Not always, scholars.

In 1793, France adopted what came to be known as the French Revolutionary Calendar. This calendar used a totally different month and week system than the Gregorian calendar we've all grown up using, and basically, January 1st in the rest of the world was something totally different in France.

This was super confusing.

And so, to alleviate said confusion and make sure everyone everywhere knew exactly which date was being referred to, the Louisiana Purchase documents list all dates in both French and Rest-of-the-World-ese.

For example, we know these documents were signed by Livingston, Monroe, and Barbé-Marbois on April 30th, 1803. According to the French calendar, April 30th, 1803, is really "the tenth of Floreal, eleventh year of the French Republic" (C2.13.3).

Yeah, it's more than a little weird.

Luckily, in 1805, France decided that having its own calendar was crazy, and it went back to the regular Gregorian calendar. But at the time of the Louisiana Purchase, both calendars were in effect, and therefore, both sets of dates were used in the purchase documents.

Looks like there were some things the purchase authors didn't want getting lost in translation.