World 31-30-30 Calendar (based on Hanke/Henry, but with Mastrofini's extra days)

**** Any Calendar Reform which proposes any extra days outside of a 7 day weekly cycle will result in a work day falling on the 7th Day Sabbath. ****
There have been two such proposals, 1 = Mastrofini - (28 day 13 month, xtra day/year, 2 xtra days/Leap Year) and 2 = Hanke/Henry (30-30-31 day 12 month, Leap Week every 5 or 6 years),
with other people reprising or offering slight variations (1 = Comte reprise, Cotsworth/EastmanKODAK reprise, 2 = World Calendar 31-30-30 xtra day/year, 2 xtra day Leap Year variation).

The Hanke-Henry Permanent Calendar (30-30-31) is an alternative to the Gregorian calendar.  It was proposed in a 2011 article by Johns Hopkins University professors Richard Conn Henry and Steven Hanke. The article was published in Arts & Sciences Magazine.

 

2001 ACE - A University web document reprising the Hanke/Henry Calendar  Suggesting the transition from the Gregorian calendar would be extremely simple:
reform could be instituted in 2006 (a Gregorian year beginning on Sunday) and only a few dates in February, March, April, May, August and December would be affected.
 
2011-12-19 - Is It Time to Overhaul the Calendar?
The calendar follows a pattern of two 30-day months followed by one 31-day month.  Memory Mnemonic - 30 days has December, March, June and September.
To account for extra time related to seasonal drift, Hanke-Henry Permanent Calendar dropped leap years and instead create a "leap week" at the end of December every five or six years.
This extra week, dubbed "Xtr", would adjust for seasonal drift while keeping the 7-day cycle on track.
"...he said, the target for complete technical adoption could be January 1, 2017, when the Gregorian year again begins on a Sunday."
(NOTE: This would be ineffective - soon people would object and want to split that extra week into days and add it on to other calendar years resulting in a wandering 7th Day Sabbath.)
 
2011-12-28 - Time for a More Sensible, Permanent Calendar?  - Pacific Standard article.
The idea actually got some serious traction in the 1950s when a proposal for a perpetual "World Calendar" came before the United Nations.
(Hanke and Henry would like to reform things even more by abolishing Time Zones.)

 

2018-12-20 - Media article reprising Hanke-Henry Permanent Calendar as it attempts to resolve quarterly inconvenience issues in the 28 day Abbe Mastrofini Calendar.
It's Time to change the Calendar once and for all 364 days per Year which has has 4 three month quarters - 2 x 30 days months and 1 x 31 day month - giving 91 days each quarter.
Additional week every fifth or sixth year.  Suggested implementation date could be 2020, 2026, 2032

 

2020 ACE - Calendar Reform Needed? The World Calender (31-30-30) - based on Hanke-Henry Permanent Calendar (30-30-31) but swapping the 30 and 31 days/month order.
The calendar follows a pattern of one 31-day month followed by two 30-day months.  Memory Mnemonic - 31 days has October, January, April and July.
The World Calendar, which starts with a Sunday, could be taken into use in a year that begins with a Sunday in the Gregorian Calendar. Such years are 2034, 2040, and 2045.
This way the transition to a new calendar would be rather invisible.

 

Common Era (CE) and Before Common Era (BCE) - https://timeanddate.com/calendar/ce-bce-what-do-they-mean.html

Any Gregorian year ending on Sunday (e.g. 2028, 2034, 2045, 2060) could be used to transition the next year to a new Calendar system starting on Monday.(e.g. 2029, 2035, 2046, 2061)

other Calendar Research references:
 

How Accurate Are Calendars? - https://www.timeanddate.com/date/perfect-calendar.html
The Roman Calendar - https://www.timeanddate.com/calendar/roman-calendar.html
The Julian Calendar - https://www.timeanddate.com/calendar/julian-calendar.html
The Gregorian Calendar - https://www.timeanddate.com/calendar/gregorian-calendar.html
The Persian Solar Hijri Calendar - https://www.timeanddate.com/calendar/persian-calendar.html
 
International Standard ISO 8601 is an international standard for the formatting of dates and times.
It has been adopted by most of the major countries around the world, either directly or as equivalent national standards.
There are a number of options in the standard but the basic idea is that a date is normally represented in the Year-Month-Day format YYYY-MM-DD
with the Year being four digits and the Month and Day both two digits. Similarly, a time is shown as Hour:Minute: Second with each being a two-digit number 24:59:59
Leading zeros are inserted as required to make each part of a date or time up to the specified number of digits. e.g. 2024-07-16 24:59:59
 
UTC: The World's Time Standard (Coordinated Universal Time) - Time Zone (Coordinated Universal Time) UTC-1 November Military