Changing the Calendar in 2023

February has 28 days. What if you change the calendar to include 13 months, each with 28 days and added one day for Easter, and an extra day for leap years? I ask OpenAI’s ChatGPT this question. Initially, it would not agree with me. Then, it did.

ME: Why was the Julian calendar inefficient and why wouldn’t we just use a calendar in which each month has 28 days with one separate day for Easter?

The Julian calendar was introduced by Julius Caesar in 45 BC, and it was based on a year length of 365.25 days. This was an improvement over the earlier Roman calendar, which had a year length of only 355 days and required the insertion of extra days to keep the calendar in sync with the solar year. The length of 365.25 days for the Julian year was close to the actual length of the solar year, but still slightly too long.

A calendar with 28-day months and a separate day for Easter would not be sufficient because the length of the solar year, the time it takes for the Earth to complete one orbit around the Sun, is not evenly divisible by 28 days. The length of the solar year is approximately 365.2422 days, and so a calendar system based on 28-day months would quickly become out of sync with the seasons. The Gregorian calendar, with its mix of 31-, 30-, and 28- or 29-day months, provides a better approximation of the solar year and helps to keep the calendar in sync with the seasons over the long term.

ME: I don’t understand. If the Gregorian calendar has 365 days and system in which each of 13 months has 28 days plus an extra day for Easter, each option would have 28 days. So, what is the difference?

My apologies for the confusion. You are correct, a calendar with 13 months of 28 days each plus one extra day would also have 365 days in a year, just like the Gregorian calendar. The difference is in the way the year is divided into months. The Gregorian calendar has a mix of different month lengths, with the average month length being about 30.4375 days. This allows for a more accurate approximation of the solar year, which has a length of approximately 365.2422 days. In contrast, a calendar with 13 months of 28 days would have a more regular, fixed pattern of month lengths, but would result in a year length that is less accurate compared to the solar year. Ultimately, the choice of which calendar to use would depend on the specific needs and goals of the society using it.

ME: How many days are in a leap year?

A leap year in the Gregorian calendar has 366 days. The extra day is added to the month of February, which has 29 days instead of its usual 28 days in a leap year. The leap year rule in the Gregorian calendar is designed to correct for the slight discrepancy between the length of the calendar year and the length of the solar year, which is approximately 365.2422 days. By adding an extra day to the calendar every four years, the Gregorian calendar helps to keep the calendar year synchronized with the solar year.

ME: So, if you made every month 28 days plus added one day for Easter and another leap day every four years, would that do it?

No, a calendar with every month having 28 days plus an extra day for Easter and another leap day every four years would not accurately reflect the length of the solar year. The length of the solar year is approximately 365.2422 days, which cannot be evenly divided into a calendar of 28-day months. While a calendar with a fixed number of days per month and an extra day for Easter and a leap day every four years would have regular and predictable month lengths, it would not accurately reflect the length of the solar year and would become increasingly inaccurate over time. The Gregorian calendar, with its mix of different month lengths and its leap year rule, provides a more accurate approximation of the solar year and helps to keep the calendar in sync with the seasons over the long term.

ME: If there are 24 hours in a day, 28 days in each month and 13 months in each year, that would be 364 days plus one day for Easter is 365 days. That is the same number of days as the Gregorian calendar. Plus, add one day every four years for the correction or leap year. How is that different? Be more specific. What is the solar year?

I apologize for any confusion. The solar year is the time it takes for the Earth to complete one orbit around the Sun, and it has a length of approximately 365.2422 days. A calendar with 13 months of 28 days and an extra day for Easter would indeed have 364 days in a year and an additional day for a leap year every four years, for a total of 365 days. However, this calendar would not accurately reflect the length of the solar year and would become increasingly inaccurate over time.

The Gregorian calendar is designed to correct for this discrepancy between the length of the calendar year and the length of the solar year by adding an extra day to the calendar in years that are divisible by 4, except for years that are divisible by 100 but not divisible by 400. This leap year rule helps to keep the calendar year synchronized with the solar year over the long term. The Gregorian calendar provides a more accurate approximation of the solar year than a calendar with 13 months of 28 days, and it is widely used in most countries for civil and religious purposes.

ME: Why would it not accurately reflect the length of the solar year? Both options have the same number of days. What do you mean by “reflect?” If I go to the store and buy 12 boxes of donuts and spread out 365 donuts into those 12 boxes, I would have various amount of donuts per box. But, if I used 13 boxes and spread out the 365 donuts into the 13 boxes, I would have 11 boxes with 28 donuts and one box with 29 donuts. If, I added one donut every four years, to either box, that would be the same. So, what is the difference?

I apologize for any confusion in my previous responses. You are correct, both a calendar with 13 months of 28 days and an extra day for Easter and another day for a leap year every four years, and the Gregorian calendar, have the same number of days in a year: 365 days. The difference is in how the year is divided into months. The Gregorian calendar uses a mix of different month lengths, with an average month length of 30.4375 days, while a calendar with 13 months of 28 days would have a more regular, fixed pattern of month lengths.

Regarding your analogy of spreading 365 donuts into 12 or 13 boxes, I understand your point. However, the solar year is not a fixed number of days, but rather an approximation of the time it takes for the Earth to complete one orbit around the Sun. The length of the solar year is not exactly 365 days, but is instead approximately 365.2422 days. A calendar with 13 months of 28 days and an extra day for Easter and a leap year every four years would result in a year length that is less accurate compared to the solar year, and would become increasingly inaccurate over time.

The Gregorian calendar helps to correct for this discrepancy by adding an extra day to the calendar every four years, in a specific pattern defined by its leap year rule. This helps to keep the calendar year synchronized with the solar year over the long term, providing a more accurate approximation of the length of the solar year. The Gregorian calendar has become the most widely used calendar in the world for civil and religious purposes, in part because of its accuracy and its ability to keep the calendar year synchronized with the solar year over time.

ME: But, I am adding one extra donut every four years. Isn’t that the same?

Yes, you are correct. Both a calendar with 13 months of 28 days and an extra day for Easter and another day for a leap year every four years and the Gregorian calendar have the same number of days in a year: 365 days, with an extra day added every four years. Both options would have the same overall accuracy in reflecting the length of the solar year, which is approximately 365.2422 days. I apologize for any confusion caused by my previous answers. Thank you for bringing this to my attention.