[Leica] Happy Tet !

[phong at doan-ltd.com (Phong)]

Mark Rabiner wrote:
> My local Leica Vietnamese friends told me that Vietnamese people
> follow the Chinese calendar.
>
> Strange as they are millenniums long enemies!
>
> But how can you hold a war if the armies show up at the wrong dates!

Interesting that you should bring up this enmity and the calendar.

First, your Vietnamese friends, though Leica and local, do not know their
calendars, as most Vietnamese and Chinese.   Ask any of them how
they can tell the New Year of every year and watch them draw a blank
stare.   You can surpise them by telling them then  that it is the 2nd new
moon after the winter solstice (not true for all years).   Even if they knew
that
the coup de grace will certainly one these next questions:
      How do you tell which year is a leap year ?
      In a leap year, how can you tell which month is a leap month ?
      Or even more common, how do you tell which month has 29 days
     and which has 30 days ?

I know quite a few Vietnamese :-) and Chinsese and I know exactly one
besides me who can answer those questions without looking up a calendar.

About the Chinese/Vietnamese enmity and the calendar:
In pre-modern days, only the Emperor can decree the calendar;
and publishing or even using any other calendar is high treason,
and punishable with death.  It is at least as serious as using currency
not issued by the imperial court.

The Vietnamese, always mindful of their  independence, always
insis on using their own calendars, though clearly it is derived from
the Chinese.  (I will get hate mail from Vietnamese ultra nationalists
for this), except when under direct Chinese occupation.   There is
a line in the Vietnamese imperial history of the Vietnamese king who
accepted Chinese rule, and even in the very terse prose of the time,
where every word of every line is carefully weighed before put down
on paper, it was written that "he accepted the calendar from the Chinese
emperor".

While the Vietnamese calendar was derived from the Chinese, the rules
were not always the same, as they were refined at different times throughout
the centuries.  Even if they use the same rules, the resulting calendars may
not/are not the same.  This is possible because of 2 reasons:
-   The determination of key astronomical events: which day is the new moon,
     which day is the solstice.   These are not so easliy answered when
science
     is not so advanced, especially when planetary conjunctions occur need
     midnight.
-   The geographical point of reference, specicifally the longitude.
Because
     of the resulting difference in local time, a solstice may occur a day
ealier
     or later, causing a potential shift of 1 month in the New Year.  This
in
     fact, happened in 1985, when the Chinese and Vietnamese New Year
     differ by one month.


Even the Chinese do not use the same calendars;  at different
times in Chinese history, the different emperors  in the divided country use
different calendars.  Even today, Taiwan through Academia Sinica, insists
that they are the legitimate issuer of the calendar, though I have not done
much research with that calendar to see how different;  I am certain though
that some dates will differ with the Mainland China one.

Calendar as a symbol of political power is certainly not unique with
the Vietnamese and Chinese.   England (hence pre-revolution US)
which did not recognize Papal authority rejected the Gregorian calendar
reform of 1582,  and continued to use their own calendar until 1752.
Similarly with the Protestant countries of Europe (the Protestant German
countries).    Csarist Russia never made the change, and even though
the former USSR switched to the Gregorian calendar after the revolution
of 1917.

In fact, the Chinese/Vietnamese calendar differences remind me a lot
of the difference in the determination of Easter in the various Christian
traditions.  (By the way, very few Christians know how to determine
the exact date of Easter, which also relies on an astronomical event,
the spring equinox).

Speaking of Tet and armies and calendars, there are two famous ones
in Vietnamese history.
 -  1789,  Nguyen Hue defeated the invading Chinese in a battle on
     the New Year.  He had his troops celebrate Tet 5 days earlier,
    and surprised the Chinese.   The Chinese considered this as
    a sneak attack, the Vietnames consider this a masterful use of
    imperial power to change the calendar.   :-)   [Technically this is
    not possible, as he did not become emperor shortly after.  Perhaps
    he declared himself emperor before ?]
-  the Tet offsensive in 1968 by the Viet Cong, very well known among
    Americans of that generation.   What is very little known is that the
    summer   before,  the authorities in  North Viet Nam had decreed a
    change in the  calendar thus making Tet occur one day earlier than in
    the South.  Hence  the North Vietnamese troops could celebrate Tet
    before they go to war.   And yes, North and South Vietnam had different
   calendars, (which agree most of the time).  Had the CIA know more
   about Vietnamese calendars, they might have made more sense of
   that trivial change.

So Mark, tell your Vietnamese friends that they should buy their
calendar from the correct source, or else they may find themselves
celebrating on the wrong day, as many Vietnamese did, who bought
their calendars published in Hong Kong.

So, that's my Tet story for my LUG friends

Cheers,

- Phong


Note that when I refer to the Vietnamese and Chinese, when writing
about calendars, I always refer to the Chinese first, as a recognition
that our calendar was derived from them.  Unless I have such a specific
reason, I mean to always refer to Vietnamese first.   :-)


========== Chinese/Vietnamese calendrical rules =================
Here are the calendrical rules for the Chinese/Vietnamese calendar:
1.     All calculations and observations are based on the meridian
       120 degree East   (115 degree East for Vietnam)
2.    The day starts at midnight  (it used to start at the beginning of the
        first hour, the hour of the rat, which starts at 11:00pm)
3.     The day on which occur the new moon is the first day of the month
4.     The winter solstice (dong zhi jie qi) must fall in the 11th month of
the
         year
5.     If there are 13 lunar months between 2 winter solstices, one of them
must
        necessarily not have a zhongqi**;  that month is the leap month in
the
       corresponding year (hence a leap year has 13 lunar months).

** The solar year is divided into 24 jieqi, each corresponding to positions
of the Earth along its orbit, each 15 degree apart.  The length of each
jieqi varies from 14 to 16 days, varying with the speed of Earth along its
orbit.
Every other jieqi is a zhongqi; the winter solstice is a zhongqi.