Which month is the last calendar month?

Explanation

A month is a unit of time. It is named after the cycle of moon phases. In the Roman Empire they introduced the a solar year in which 12 months is equivalent to one year from spring to spring. This introduced fixed lengths of months which did no longer fit with the Moon's orbital period around Earth. The months of the year are called: January, February, March, April, May, June, July, August, September, October, November and December.