**Christian Era and Universal Time**

**Our era is the Christian Era (see
p. 69), but nobody knows precisely when Jesus was born. Nevertheless, in
AD 525, more than five centuries after Jesus’ birth, the first year of our
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 Appendix I p. 103‑105).
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). So Dionysius Exiguus’
chronology is only imperfect insofar as its first day is not the day Jesus was
born.**

**By counting the days and measuring the so called Universal Time UT (see p. 40), we measure the total time
elapsed since the beginning of our era. Strictly speaking, the beginning of the
Christian Era is the Greenwich midnight point in time with which the first day
of the first month (January) of AD 1 began; therefore, the moment of the
beginning of our era can be represented by a notation like [1‑1‑1; 00:00:00].
Similarly, each moment of our era can be represented in terms of date and point
in time. ****Thus we are
provided with a somewhat irregular but nevertheless perfect chronological
system based on the Christian Era and the Universal Time.**** For example, [21‑3‑140; 14:17] represents a moment,
called spring equinox, at which in the northern hemisphere spring began (see
p. 41). The same holds for [20‑3‑325; 10:02] (see
p. 44) and [20‑3‑415; 05:18] (see p. 45).**

**Nowadays, for practical scientific and economic reasons, extremely
accurate atomic clocks are used to generate the so called Coordinated Universal
Time UTC, which is continuously such a close approximation of the Universal
Time UT that |UT – UTC|, being the absolute value of their (continuously
irregularly fluctuating) difference, never exceeds 1 second. Thus,**

**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 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 (therefore) 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, owing to the prolepticity of the Julian calendar,
it is only since somewhere in the twelfth century BC that the spring equinox,
which marks the beginning of spring in the northern hemisphere, falls in March.
As a matter of fact, at the (abrupt) beginning of the Holocene (around 9700 BC)
****the spring equinox fell only in
June. From somewhere in the ninetieth to somewhere in the fiftieth century BC
it fell in May, from somewhere in the fiftieth to somewhere in the twelfth
century BC in April.**

**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 very
first turn of the year must have been [1‑1‑2; 00:00:00],
because it came one second after [31‑12‑1; 23:59:59].
Analogously, the very first turn of the decade must have been [1‑1‑11; 00:00:00],
because it came one second after [31‑12‑10; 23:59:59].
Analogously, the very first turn of the century must have been [1‑1‑101; 00:00:00],
the very first turn of the millenium [1‑1‑1001; 00:00:00], the
second turn of the 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), its first year 2001 (not 2000).**

**© Jan Zuidhoek 2019‑2020**