A brief annotated history of the relevant events that shaped the modern calendar

Abstract

I present the results of a compilation of the most relevant historical facts that determined the evolution and form of the Gregorian calendar since its earliest recorded origin. This compendium, in the form of a brief chronological annotated history, gathers in one place all the answers to the most frequently asked questions about the characteristics and peculiarities of the modern calendar, including the origin of the names, the order and length of the months, and the presence of years with different lengths. It also disproves some falsehoods on the subject. This article responds to the need to gather in a single orderly writing all the relevant factors on the subject that are usually explained in a scattered, partial or disjointed way in separate sources. This article is proposed as a verified source on the subject and can be used as support material in the classroom or for dissemination. Many of the sources consulted are electronic, but everything obtained was contrasted with several verified bibliographic sources on the subject of calendars. This compendium highlights how the human effort to keep the length of the calendar year synchronized with the passing of the seasons was affected in the western world not because of technical or knowledge limitations, but because of external factors that were imposed over the concrete objective of a calendar.