So as of 1905: time is relative and slows as the speed of light is approached. Calendars are a graphical representation of the passage of time based on the motion of the planets, segmenting time into days, weeks, months, and years. We now enter an age when for the first time in history precision in how we keep time becomes critical. With the advent of train travel over longer distances it became important for clocks in various cities to strike the hour at the same time. Also, if you are trying to coordinate the sharing of a single track between multiple trains, prior to the invention of radio communication, synchronized time is a matter of life and death.
As industrialization and urbanization accelerated in the late 1800’s and early 1900’s the standardization and synchronization of time over distance became an important challenge to engineers. The French genius Henri Poincare was a driving force in this area. The first attempts at synchronizing clocks in a large urban area occurred in Paris using pressurized steam to pneumatically blast clocks all over the city into some semblance of synchronicity. An elaborate system of tunnels and steam pipes was developed throughout the City. Later, as the telegraph expanded its reach, the much higher speed of an electrical signal was used to synchronize clocks over large areas.
In 45 BC, Julius Caesar inaugurated the basic calendar we use today. However, his calendar was flawed in that it did not align precisely with the rotation of the planets. Over many years, this creates a misalignment between human seasonal celebrations and the weather. For instance, after many years of being off by a day or so, a misaligned calendar might cause a fall harvest celebration to be scheduled for the middle of the summer. Nearly 1,500 years after its debut, the Julian calendar required a 10 day correction.
Around 1,000 A.D. Ptolemy observed in a published article that the Julian calendar was off, but at this time and for hundreds of years to come, it was potentially life-threatening to question the validity of the calendar. In the 13th century, the western world’s view of the universe was dictated by the Roman Catholic Church. The Roman Catholic Church did not recognize that the earth circled the sun, and in order to work out a truly precise calendar, this bit of dogma would have to adjust to match reality. So it should be no surprise that in the 1300’s it was the outcaste, curmudgeonly, genius, monk with superhuman intellectual abilities and independence, Roger Bacon, in league with Pope Clement IV, who died too young, set the stage for the Gregorian correction of the 1500s. While history does not record the reasons behind Clement the IV’s interest in calendar reform it was his interest and advocacy which propelled Roger Bacon to document the failings of the Julian calendar. Shortly after Bacon’s work reached the Pope, the Pope died, leaving Bacon behind with plenty of knowledge but no power to do anything about it.
It is also important to our overall understanding of the evolution of calendars through history to bear in mind that the telescope was not invented until the 1600’s. It was the telescope and minds like Galileo and Copernicus that literally reoriented the universe. This reorientation of the universe leads to a better understanding of the motion of the planets and the place of the earth in the solar system.