Almanacs from the Civil War era reveal how two sides of an embattled nation used data from the natural world to legitimize their claims to statehood.

The complicated system that determines the High Holy Days is a relatively new creation, dating to around 350 CE.

Everybody remembers that the Ides of March was the day Julius Caesar was assassinated. But what does it mean, and why that day?

Many scholars contrast linear and cyclical time and note that cycles were an important part of Maya concepts of temporal reality.

Why do we celebrate the beginning of the New Year on the first of January? Julius Caesar, mostly.

The 1752 British transition from Julian to Gregorian calendar added 11 days to people's lives.