Wouldn't a Thirteen-Month Calendar with 28 Days Make More Sense?
This is a complex question. The answer is also complex. The short answer is that we do always have and to in limited circles as we always have done. Certain Japanese, Native American, and Icelandic (Nordic) Viking descendant groups continued to practice the ancient 13 month pagan calendar up into the modern era. This calendar is the true human calendar which has been practiced by all indigenous communities prior to the age of European and Middle Eastern Imperialism.
The 13-Month Calendar: An Ancient Expression
The 13-month calendar is an ancient expression that interlocks with the common 13-dedity paganism practiced worldwide. The earliest examples are from the Ancient Sumerian Civilization in modern Iraq. From here, all civilizations expanded outward. The 13-god pantheon found in Greece, India, North America, Africa, South America, Hawaii, and among the Druids, originated from this original pagan pantheon.
Evolution or Revolution?
Around 1177 BC, there was an invasion force that destroyed much of Egypt and overthrew certain institutions. In this same period of time, the Hebrew people were taken as slave hostages to Babylon by Nebuchadnezzar, a ruler with a name that could be relevant today. Babylon was built on the ruins of Sumerian and Akkadian civilization, borrowing their languages and religions. Hebrew slaves didn't care much for their pagan overlords and actively resisted assimilation into the culture.
The Babylonian Sexagesimal System
The structure of time as we know it and the division of 3,600 seconds in an hour, 24 hours in a day, and two 12-hour periods all go back to the sexagesimal system employed in Babylon. This is quite different from a 10-based digital system. The sexagesimal system is based on the number 8, not 10: 8 fingers, three knuckles per finger, two hands 48. Many of the numbers and multiples in this system are still culturally significant even 3,500 years later.
The Hebrews and the Babylonians
The Hebrews were already a universally literate people, which contrasted harshly with the slave culture practiced in Babylonian society. As a result, most of the Hebrew slaves ended up working as scribes. Right away, this posed problems for the rulers of Babylon. Essentially, the Hebrews, being very orderly, found enough flaws in the system to begin changing it slowly. Revolutionary change begins with evolutionary change. So, 13 is not an easy number for dividing up the hours of the day. For centuries, 13 has been considered an unlucky number, such as Friday the 13th, a baker's dozen, etc. This is because they gave 13 the chop.
The Babylonian Pantheon and the Hebrews
Ishtar and Marduk were merged, their cultic idols combined, and a longer month created. This is discussed in the Book of Esther. Ahasuerus (Artaxerxes) or Smerdis allegedly found this new wife of his Esther (Isis, Ishtar, Amestris) and was promised her by her Uncle Mordecai (Mardukka, Marduk). So Esther is likely a priestess of Ishtar, and Mordecai is the last priest of Marduk. Their cults and respective formal statuses are absorbed by the new cult of Nabu, a descendant of Marduk, in the story that governs the pantheon.
The Impact of the Babylonian System
The clocks have 12 hours, and Marduk wears a clock with gears around his neck in every depiction. So back to the dissident Hebrew scribes, they realized the mathematical sense that 12 made over 13 and selectively rewrote the Babylonian pantheon from the inside as the educated scribes that controlled the entire system. Thus, everything revolves around 12: 12 months, 12 deities, 12 hours per half day, 12 prayer zodiacs, and they align. However, this system is wrong and causes our days to fluctuate from year to year. Under the old calendar system, feast days for various holidays would be on the same date and day of the week every year. By Ancient Sumerian standards, this newly "improved" 12-month system was literal chaos.
The Persistence of the 12-Month System
Somehow, though, we have been stuck with it for over 2,500 years. This makes little sense, and the idea that we keep it is beyond insanity. Instead, some machine shops operate on fixed two-week pay cycles on 4-week financial months for 13 accounting periods.