The calendar used in Britain is the gregorian calendar, made in October 1582 following the papal bull Inter gravissimas by Pope Gregory XIII, and bears 12 months making a year. The main shift was rereckoning leap years, heeding truer to Earth revolving about the Sun, which is 365.2425 days long, closer to the "sunly" year, which is 365.2422 days long. 

"Every year that is exactly divisible by 4 is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is. "

-United States Naval Observatory.

However, although hard work to reckon the gregorian calendar was good, there is still room to greaten it to behove everyone in British society, something that seems small but shall have a good, big impact, and that is to eke a 13th month. This is not a new thought, for this was thought up and outstandingly reckoned by Moses Cotsworth (1859-1943), a business accountant and analyst, who crafted it whilst working for a railroad business. He wanted to make the year easier, simpler to learn, follow, and understand, more straight forward for all. The current gregorian calendar drifts overtime, holidays like Easter are always shifting date, days that fell on one weekday one year do not fall upon those days again the next, and this is why we should update it one last time, so there is no need to wend and reckon the year every time. But what are the advantages of the 13 month calendar year, how does it work?

ADVANTAGES:

Each and every month has 28 days (4 weeks), starting on a Sunday and ending always on a Saturday, and every day of a month falls on the same weekday in each month (e.g. the 17th always falls on a Tuesday). This is found by taking 364, sundering it by 13, yielding 28 for each month's days, leaving us with a bonus day to be our new year's day, belonging to no month, which shall be explained below. 

Every year has 52 weeks sundered among 13 months, and thus every year has 4 even-lengthed quarters, made up of 91 days (13 weeks or 3 1⁄4 months).

The calendar is the same every year, unlike the gregorian calendar, which differs from year to year. Hence, scheduling and planning will be easier for institutions and industries with lengthened production cycles, as well as for us. As well as this, movable holidays celebrated on the nth weekday of a month, such as our beloved Easter holiday, would be able to have a fixed date while keeping their traditional weekday.

Supporters of the International Fixed Calendar have argued that 13 divisions of the year are greater to 12 unequal divisions in terms of monthly cash flow in the economy.

Statistical comparisons by months are more true, since all months hold the same number of business days and weekends, likewise for comparisons by 13 week quarters. As a likely side benefit too, the menstrual cycle of women can be better reckoned, since it is often said to be 28 days long, albeit true that there is variation between some women. Still, thirteen 28 day months might be good for tracking periods and fertility with more ease, followed with other things medical. 

For holidays this calendar would behove many faiths too, such as Islam, Christendom, Heathendom, and more if they lean on a more moonly way of reckoning time for their holidays, but without a doubt the more worldly and everyday holidays shall be benefited too. 

Reckoning and dating solstices and equinoxes will be effortless, since they will always fall on weekends, on the utter same day always as well, with March 7th being the spring equinox, September 21st the autumn equinox, the 14th of the new month the summer solstice, and the winter solstice the leap new year day, which is explained below.

The calendar months, being 28 days each, would line up highly close to the cycles of the name sake of the word month, the Moon, so learning when a new Moon, full Moon, or crescent Moon will come about will be utmost easier with the 13 month calendar. 

This new 13 month year calendar would be better for farmers in wanting to plan how and when they plant and reap their crops, or when livestock gestational times and care are right. 

The last advantage to having this fixed calendar of 13 months for Britain is rather straight forward, it would be cheaper to buy calender since we would not need year specific calendars to hang up on our walls anymore, only bespoke calendars with whatever style or art you want for your calendar.

DISADVANTAGES:

Birthdays, significant anniversaries, and other holidays would always be on the same day of the week. This could be seen as problematic for public holidays that would fall on non-working days under the new system: For example, New Year's Day and International Labor Day are all celebrated on the first day of their respective month, which under the International Fixed Calendar would always be a Sunday, a non-working day, so folk might want to be compensated with another day off.

Everyone's birthdays, as well as holidays and dates of weight would need to be reckoned again into new dates, if we want to have the right, same time of the year for each. How we reckon the new dates are thus: take the total days of the months leading up to that date before the switch, and that shall give you a total of how many days INTO the year a date needs to be in the new calendar. For example, March 2nd, 1971, as a date would be rereckoned as 31+28+2=61 days into the year from when it begun, so yielding May 5th as the new date, since 31 days are in January so far, and 1971 was not a leap year, so add 28 from February and 2 from March. This would mean we would need new birth certificates and the likes after the shift, if we did not artificially keep the number of dates, however, this will help folk whose birthdays befall the 29th, 30th, or 31st of a month too. 

HOW WE MAKE THIS WORK:

To make the 13 month calendar year work, we need to first add a new month, and that month, in keeping with the Roman namings of our months already, shall be named Sol, after the sun, and it shall be stowed between the months of June and July.

Every four years there will still be a leap year day, and for it to still work with the calendar, we must make this day fall on the summer solstice, however, it will not be the 14th of Sol it will fall on, it will be afterwards, but before the 15th, for this leap year day will be a hollow day, or day belonging to no month, thus making the weekend of that time of month have three days, not two, since every solstice and equinox shall fall on a weekend anyway, and altogether this helps keep the month right and true.

For "new year's day" to work, whilst not throwing out the calendar, it must be a hollow day, a day belonging to no month as well, and made one in the same as the winter solstice, coming after the 28th of December, but before January 1st. This is further given legitimacy by how many of our forebears long ago did likewise, seeing the winter solstice as the "new year's day" as it was a liminal time of rebirth as it still is today.

To make this calendar year work, we would have to drop 10 days from whatever year we choose to take up the 13 month calendar. To not screw up the holidays the new calendar would have to start its first fixed day upon January 11th, and also be a year where the winter solstice, before adoption, befalls Saturday, so as to not break the weeks in a way that diminishes the new 13 month year.

HOW COME IT WAS NOT CHOSEN ALREADY? 

Well, it nearly was. Cotsworth's fixed 13th month year calendar was picked among 130 calendar proposals by the League Of Nations to be further talked over and considered for adoption, however, it was dropped in 1937 since it did not win final approval, however, businesses like the Eastman Kodak Company did use it well beyond the 1930s into the 1980s, finding it useful and better for business.

TO SUM UP

The new year would be made of 13 months, each 28 days long. 

The leap year day every four years must be on the summer solstice and be a day belonging to no month at all. 

The "new year's day", or year day, must be the winter solstice and be a day not belonging to any month at all, coming after December 28th, but before January 1st. 

This would be better for everyone and business, and everything to do with reckoning and living within the year will be easier too. 

PLEASE HELP

If you have read all of this and find yourself not against it, please sign so we Brits can beseech our government to make the shift to a greater 13 month calendar year. It has been a long time waiting, with this calendar life will be simpler with all things timewise, the year, and the universe, looking back at all the advantages already listed, and we are the bringers of change, if we do not do this no one else will.