Universal Time and Coordinated Universal Time
In the final analysis, the Universal Time, abbreviated to UT, is nothing but the time elapsed since the beginning of our era.
Our era is the Christian era, but nobody knows precisely when Jesus was born. Nevertheless, in AD 525, more than five centuries after Jesus’ birth, the first year of the Christian era (AD 1) was retrospectively and implicitly but nevertheless exactly and definitively laid down by the learned Scythian monk Dionysius Exiguus (see p. 69), by means of his Paschal table (see Dionysius Exiguus’ Paschal table). Therefore, most Christians believe that Jesus was born either on 25-12-1 or exactly a week before 1-1-1. For example, Charlemagne must have believed that He was born exactly a week before 1‑1‑1, because he let himself crown emperor on 25‑12-800. However, according to modern historians, Jesus was born some years before the beginning of the Christian era, and died at 3‑4‑33.
Strictly speaking, the beginning of our era is the Greenwich midnight point in time 00:00:00 with which the first day of the first month of AD 1 began. Therefore, the beginning of our era can be indicated by [1‑1‑1; 00:00:00]. The Universal Time can similarly be indicated in terms of date and point in time. Nowadays, for practical reasons, extremely accurate atomic clocks are used to generate the Coordinated Universal Time, abbreviated to UTC, which is continuously such a close approximation of UT that |UT – UTC|, being the absolute value of their (continuously irregularly fluctuating) difference, never exceeds 1 second.
Keep in mind that in the framework of our era Thursday 4‑10‑1582 was the very last Julian calendar day, and that that Thursday was immediately followed by Friday 15‑10‑1582 being the very first Gregorian calendar day. As a result, the year 1582 had only 355 days. Thus that year is the only calendar year of our era which had a number of days which is not 365 (which is the number of days of any normal calendar year) or 366 (which is the number of days of any leap year). Between the beginning of our era and the present year 2020 there were only four calendar years of our era whose year number was divisible by 4 but whose number of days was nevertheless 365, namely AD 4 and the years 1700, 1800, and 1900. This implies that 1‑1‑1 was a Sunday, which simple fact can easily be derived from Annianus’ 532-year Paschal cycle being part of Beda Venerabilis’ Easter table (see Appendix II p. 106-120).
Keep also in mind that our era consists of the years AD 1, 2, 3, …… and the years 1, 2, 3, …… BC, on the understanding that:
1) the ones after the year 1582 are considered to be Gregorian calendar years;
2) the ones before the leap year 45 BC and the ones between the leap year AD 8 and the year 1582 are considered to be Julian calendar years;
3) between the leap years 45 BC and 9 BC there was (erroneously) a leap year every three years (instead of every four years) and (in consequence) between the leap years 9 BC and AD 8 there was no leap year at all (instead of a leap year every four years).
Keep also in mind that between 1 BC and AD 1 there was no AD 0 or 0 BC. The first year of our era was AD 1, and its first day 1-1-1. The first turn of year must have been [1‑1‑2; 00:00:00], because it came one second after [31‑12‑1; 23:59:59]. Analogously, the first turn of decade must have been [1‑1‑11; 00:00:00], because it came one second after [31‑12‑10; 23:59:59]. Analogously, the first turn of century must have been [1‑1‑101; 00:00:00], the first turn of millenium [1‑1‑1001; 00:00:00], the second turn of millenium [1‑1‑2001; 00:00:00]. As a consequence, the first day of the third millennium was 1‑1‑2001 (not 1-1-2000) and its first year 2001 (not 2000).
© Jan Zuidhoek 2019-2020