Archive Magazine CD 1995/Archive Magazine CD 1995.iso/discs/pipeline/abacus/p_line/Calendar/ReadMe

Text File | 1994-04-17 | 9.4 KB | 184 lines

%OP%VS4.13 (28-Apr-92), Gerald L Fitton, R4000 5966 9904 9938
%OP%DP0
%OP%IRY
%OP%PL0
%OP%HM0
%OP%FM0
%OP%BM0
%OP%LM4
%OP%FS14000
%OP%PT1
%OP%PDPipeLine
%OP%WC1026,2262,304,1748,0,0,0,0
%CO:A,72,72%
%C%An Everlasting Calendar
%C%by Gerald L Fitton
Keywords:
Calendar Julian Gregorian Year Month Day Spreadsheet Fitton

Some History

Before the year 46 BC all twelve months of the year except February had
either 29 or 31 days.  February always had 28.  Most years had 355 days
but, every so often the priests or politicians added an extra month in
order to keep the seasons (particularly the Spring equinox) at or about
the same time of the year every year.  It was Julius Caesar who first
tried to bring some regularity to the calendar.  He ordered that the
year 46 BC should have 445 days (to bring the Spring equinox close to
the beginning of the Roman year ie in March) and that every year
thereafter should have either 365 or 366 days.  The extra day was to be
added to the 29 days of February in every fourth year to make it a 30
day month.  So you'll see it was thanks to Julius Caesar that we have a
variable length for February.  He chose February because it was the
last month of the year. The calendar was slightly modified by Augustus
Caesar (who followed Julius Caesar).  He renamed August after himself
(otherwise we might have had a Sexember) and added an extra day to his
month making August 31 days by reducing February to 28 days (except in
leap years).  Further, in an attempt to fine tune the Spring equinox,
he decreed that the first leap year should be 8 AD so that 4 AD and
earlier fourth years were not a leap years.  His calendar for 8 AD was
like that of any of our leap years today.

The Earth does not take exactly 365 days and 6 hours to go round the
Sun.  If it did then the Julian calendar would keep the seasons in
synchronism with utter perfection.  It takes about 11 minutes per year
less than this.  Over the centuries since 8 AD these eleven minutes per
year added up so that, by the year 1582, the seasons had slipped by
about ten days.  Pope Gregory XIII was more concerned about Easter
(which I think is on the first Sunday after the first full moon after
the Spring equinox) and the other movable church festivals than about
the farmers, and decreed that ten days should be dropped from the year
1582.  The Roman Catholic countries adopted this Gregorian calendar
almost immediately but Protestant countries were slower to accept it.
In order to prevent a later problem with the accumulating 11 minutes
Pope Gregory ordered that century years such as 1800, 1900 and 2100
should not be leap years unless, like the years 2000 and 2400, they
were divisible by 400.

In Britain we continued to use the Julian calendar until 1752 by which
time the 'error' amounted to eleven days.  In Britain in the year 1752
the day after the 2nd September 1752 was the 14th September 1752.  This
unique September is produced by this spreadsheet.  Some countries were
even later than Britain in accepting the Gregorian calendar.  Bulgaria
adopted it in 1916 and the Soviet Union in 1918.  The Greek Orthodox
Church finally accepted it in 1924.  So you can see that for the years
1582 to 1752 there was a discrepancy of 10 or 11 days between Britain
and the Catholic countries.  During that period this calendar
spreadsheet is correct only for those countries that continued to use
the Julian calendar.  If you have the knowledge and expertise to modify
this spreadsheet for another country then let me know and I'll include
it on a future PipeDream 4 disc.


How to use the spreadsheet

PipeDream 4 saves the position of the caret with the document.  This
calendar spreadsheet has been saved with the mouse in slot N2.  If the
caret is not in that cell then use the mouse to position it in cell N2.
This contains the year as 1991.  Type in another year, for example
1066, and tap <Return>.  There will be a delay whilst the spreadsheet
recalculates.  The Battle of Hastings was on the 14th October 1066 and
you will see that it was a Saturday.  My History teacher had a theory
that all wars broke out at 3.00 pm on Sunday afternoons when everyone
had just got out of the pub!  We went to war with Germany on the
3rd September 1939.  I can't remember when Pearl Harbour was attacked
by the Japanese but I seem to remember that was a Sunday afternoon,
possibly the 7th December 1941 at about 3.00 pm.  The Spanish Armada
was on Friday the 19th July 1588.  My History teacher would have loved
to find out what day of the week the Bastille was stormed and there may
be some who want to know what day of the week the original St Swithan's
day was on.  Contributions to this discussion will be welcome,
particularly if you know the date of some important events.

Some people had a problem with this calendar using PipeDream 3 if they
used as their default brackets for negative numbers.  With brackets,
positive numbers have a trailing space after every number.  The space I
have allowed for the calendar dates is not wide enough to accept
brackets as the method of indicating negative numbers.  I believe (but
I'm not sure) that with PipeDream 4 the options are always saved with
the document.  If this is not the case and you see %PC% signs instead of
numbers then please change your default to negative signs (use <Ctrl O>
to open the options dialogue box window) and please let me know!


How it works

Cell W6 contains a key formula that returns the day of the week
(numbers 0 to 6 representing Sunday to Saturday respectively) for the
1st January of the year in cell N2.  Actually it's two slightly
different formulae, one for the years before 1752 and one for the years
after 1752; an 'if' is used to decide which formula is used.  The
formula uses the year entered into N2 as input and calculates the
number of days between a fixed date (eg 1st January in the year 1 AD)
and the year chosen (in cell N2) by counting 365 days per year plus an
extra day for every leap year.  This number of days is divided by 7 and
the remainder used to decide on what day of the week the 1st January
fell for our chosen (N2) year.  In cell X6 the date for the first
Sunday in January is calculated (using W6 as input).  A number between
2 and 8 (inclusive) is returned.  The formula in V7 for the number of
days in February looks complicated but all it does is to work out
whether the year is a leap year or not and returns either 28 or 29
appropriately.

In the X column the date of the first Sunday of each month is returned
for all twelve months.  It is the values in this column which form the
input to the visible part of the calendar.  I don't know why exactly,
but, until I added in a 0.5 before using the function int (integer), I
occasionally got wrong values in PipeDream 3.  I haven't checked
whether the same problem arises in PipeDream 4.

Cell C9 contains the date of the first Sunday in January taken from X6.
By a process of adding 7s (eg cell D9 contains C9+7) the remaining
Sunday dates in January can be found.  An 'if' is used in the first
week of the month to avoid negative dates and, at the end of the month,
another 'if' is used to prevent values greater than the number of days
in the month appearing.  September is treated differently from the
other months.  The year is tested to see if it is 1752.  If not then
the standard formula is used, if the year is 1752 then the special 1752
values are entered.  Cell V14 (which contains the number of days in
September) also has an 'if' which tests whether N2 (the year) is 1752
or not.

I have to confess I made a bit of a mess of choosing the best way of
replicating each month so I have got rid of all the $ signs (which fix
the replication) in order to hide my embarrassment.  I got rid of the
$s by using <Ctrl>+BSE (search and replace) to replace the $ signs with
nothing.  So now you can't see what a mess I made of my choice of where
to put the $s!

Cell H5 contains a hidden error message triggered by an 'if' if you
enter a year before 5 AD.


Customising

You can insert rows and columns with impunity.  All the cell references
change automatically.  Be careful about deleting rows, parts of rows or
columns.  Don't use the master copy!  You can add your own graphics etc
and print calendars for all your friends.  Finally you can use
'Snapshot', <Ctrl>+BSS, (and then delete columns T to Y) to make a
simple calendar for a chosen year that can be customised without fear
of damaging any formula.


Printing

Some people do have problems printing this calendar because the
columns T to Z cause a 'wrap around' and destroy the layout of the
first few months.  I could have taken the easy way out and completely
hidden columns T to Z by making them zero width.  Then nobody would
have printing problems but you might find that you can't open up the
'missing' columns.

Anyway here is what I have done and how to fix it if the printing does
go awry for you.  Load the calendar and then double click on the
command file [ZeroWidth].  This reduces the width of all columns to the
right of S to zero width.  Your printing should be OK now.

I prefer to print out using Outline fonts rather than the PipeDream
printer drivers.  I suggest that you use a sans serif font such as
Acorn's Homerton.Medium (Helvetica) or Beebug's Vogue (Avant Guarde)
rather than one of the serifed fonts such as Trinity.Medium (Times) or
Paladin.Roman (Palatino).  You can get some interesting effects with
decorative fonts such as EFF's Hot Dog or Horror!