**This**** webpage belongs
to www.alexandriancomputus.net,
which is a website promoting [Jan Zuidhoek
(2019) Reconstructing Metonic
19-year Lunar Cycles (on the basis of NASAs Six Millennium Catalog of Phases of the Moon): Zwolle], and
concerns the relation between
the fundamental concepts Christian Era and Universal Time.**

**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 on 25**‑**12**‑**1 =
25 December AD1 or exactly
a week before 1**-**1**-**1 = 1 January AD1. 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. 23),
we measure accurately 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 1‑1‑1 began; therefore, the moment (comprehending date and point in
time) of the beginning of our
era can be represented by a notation like [1‑1‑1; 00:00:00]
or like [1 January AD1; 00:00]. Similarly,
each moment of our era can be represented
in terms of date and point
in time, for instance
moment [21 March AD140; 14:17]. Thus we are provided with a somewhat irregular but nevertheless
perfect chronological system
based on the Christian Era and the Universal
Time UT.**** 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,**

**By**** definition,
the ****Central European
Time CET is UTC + 1 hour, the Central European Summer Time CEST is
CET + 1 hour. This
implies that the Central European Summer Time CEST is
UTC + 2 hours.**

**Keep in mind that
it is the local Greenwich time which is exactly equal to
UT. This implies, for example, that
the local Liverpool
time is UT ̶ 12 minutes,
the local Rome time is UT + 50 minutes, and the local Alexandria time is UT + 120 minutes. For example,
Julius Caesar was murdered on 15 March 44BC probably sometime between 10:30 and 11:50 local
Rome time, so round about [15 March 44BC; 10:20].**

**Keep also 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 2021 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 (relatively very 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 2019-2021**