Contents of the GC.DOC file
* G E O - C H R O N *
* Version 1.0 *
* (C)opyright 1986 *
* All Rights Reserved *
* GeoGraphics Software *
* 126 Mountain View Road *
* Glastonbury, CT 06033 *
* GeoChron is user-supported software provided to *
* you at no charge on a trial basis. If you use this *
* software and find it of value please register your *
* copy for $15.00 and support the shareware concept. *
* Registered users will be provided with information *
* about program updates. Please make checks payable *
* to G. K. Marek at the above address. *
* You are encouraged to share this software with *
* others provided that it is distributed complete *
* with documentation and in unmodified form and *
* that no fee or other consideration is charged or *
* accepted. All commercial, business and government *
* users must register each copy in use. *
* We hope you enjoy using GeoChron. Your comments and *
* suggestions to improve this product are always welcome. *
GeoChron is a program which tracks and displays the local
time in as many as 43 cities all around the globe. Unlike
other programs of this type, GeoChron accounts not only for
time zone effects but also for daylight savings time at each
city. Information is provided on a full-screen color non-
graphics display. Windows and menu-driven commands are used
for program modifications. Program options provide users
with the ability to tailor the display for their specific
needs. As many or as few cities as desired can be displayed.
Military or 12 hour clock can be selected and the layout of
the world map can be varied to suit the user. Additional
program features include time zone differences and great
circle distances between cities and a special alarm feature
which can be set for any world city time.
This program is designed for IBM Personal Computers and
close compatibles. It will execute on the IBM-PC, PC-XT, and
PC-jr. DOS Version 2.1 or later is required. GeoChron does
not require an internal clock and will accept the time set by
you during DOS boot-up. Of course, the use of the internal
clock will allow for automatic timekeeping.
Since the program relies extensively on color, a color
monitor is recommended. The program will run, however,
unmodified, on the Compaq. GeoChron requires about 64K of
memory and does not require BASIC to operate.
The GeoChron system comes in four files:
GC.EXE executable program module
GC.DAT default settings and cities information
GCDAT.BAK a back-up duplicate copy of GC.DAT
GC.DOC documentation file (ASCII); (this file)
The first two files must reside on the current directory or
path for the program to be accessible.
None of these files is copy-protected and it is suggested
that a set of backup files be made and saved in a separate
place with your other archive and backup files. Save all
four files in their original state to preserve initial
program default settings and cities information and to have a
complete package to provide to other users.
GeoChron is executed from the current directory or path with
this command at the DOS prompt: GC
There are no optional arguments.
Upon execution, GeoChron will load from the current
directory and access the GC.DAT data file to load current
settings and cities information. Once the program and data
are loaded, the program no longer requires these files unless
a new configuration is filed to disk for future use. The
program is virtually self-explanatory and uses menus
extensively. The program will load into [AutoTime] mode
incorporating the default values and cities information in
GC.DAT at time of execution.
GENERAL PROGRAM FEATURES
GeoChron generates a stylized world map with cities
indicated by three letter codes. The map is divided into 24
time zones each of which is further divided into three
twenty-minute segments. One timezone, normally the one you
are in, is specially designated as the "local" timezone. The
local timezone (initially set by the program defaults to New
York) is indicated on the top scale by a magenta symbol.
Time and date details about the local time zone as indicated
in the center of the black area below the world map. The
local time indication is standard time if it is shown in
yellow and daylight savings time if it is shown in brown.
The black background on the map itself indicates the portion
of the globe between 6PM and 6AM (that is, approximately
"nighttime") and moves with the time in twenty minute
intervals. A gray band will appear momentarily around the
display border while the map is being updated. Cities are
indicated on the map in bright yellow if they are presently
on standard time and in brown if they are presently on
daylight savings time.
Across the bottom of the world map is an hour-day scale with
some features in white and some in yellow. The white (upper)
scale indicates the STANDARD time in that particular world
zone. One point on this top scale is the yellow letter M
which represents midnight; N indicates noon. The lower
scale, in yellow, is in the form:
<< Sun | Sat >>
and is used to determine the day of the week for any time
zone. The symbol | represents the International Date Line in
the central Pacific Ocean. From this symbol to the left
(west), it is Sunday until the M (midnight) symbol is
encountered on the scale above. It is Saturday toward the
east until the M symbol. Of course, the scale wraps at the
left and right edges of the map.
A WORD ABOUT TIME SYSTEMS
GeoChron displays time using the standard US AM/PM 12 Hour
Clock and the International (or Military) 24 Hour Clock.
However, for simplicity, all INPUTS to GeoChron must be
given using the 24 Hour Clock (the same as DOS). Some
examples of the relationships between the two systems are
US/12 Hr Intl/24 Hr Input Input
MIDNIGHT 12:00 AM 00.00 00:00:00 0000
12:37 AM => 00.37 00:37:00 0037
1:24 AM 01.24 01:24:00 0124
11:08 AM 11.08 11:08:00 1108
NOON 12:00 PM 12.00 12:00:00 1200
12:15 PM => 12.15 12:15:00 1215
3:59 PM 15.59 15:59:00 1559
11:49 PM 23.49 23:49:00 2349
The ACTUAL local time (whether daylight or standard) should
be input and GeoChron will take care of the rest. If you
have an internal computer clock, you must set it forward and
back during switches between daylight and standard time just
as you do with your other clocks.
Some computers have clocks that lose the seconds when time is
reset. For example, the time 10:15:53 would be set to
10:15:00 and 53 seconds would be lost. In these cases time
adjustments should be made just after the minute has turned
to minimize time loss effect.
GeoChron incorporates a number of special features and
options which are explained below. These features are
accessed by selecting the letter [F] from the [AutoTime]
mode. Some features require that a particular world city be
identified. Each city has been assigned a three letter
abbreviation. City codes must be referred to in CAPITAL
letters (NYC, not nyc) to be recognized by the program.
The GeoChron alarm can be set for a specific time in a
specific world city. This could be the local time or the
time in a foreign location. For example, assume that you are
in New York. You can set the clock to ring when it is 7PM
(1900) in Paris without having to compute time differences
simply by indicating PAR and 1900 when the alarm is set.
GeoChron keeps track of the timezones and any savings time
that might be in effect at either city.
Activating the alarm will illuminate a note in the lower left
corner of the screen. The alarm will ring at the appropriate
time, chiming every five seconds for one minute or until any
key is selected to stop it. The alarm will be turned off
once it has rung and will have to be activated again even to
ring again at the same time on the next day. The command
[Activate] will engage the alarm with the current settings
unchanged. The [LOC] city code can be used for local time
alarm. Be sure to input the alarm time in HHMM format, two
digits for the hours and two for the minutes using a 24 Hour
The [TimeZones] feature allows you to check the number of
hours (timezones) any city is ahead or behind any other. A
base zone is initially set to the local city but can be moved
to any other city, one zone at a time, with the [W]est or
GeoChron can also compute the distance between any of the
cities in the program database (not just those shown on the
map). A listing of cities can be selected. The distance
shown is the "great circle distance," which is the shortest
distance between the two points on a globe. This distance is
provided in statute miles (ordinary measure) or in nautical
miles, a system used extensively in aviation. One nautical
mile is about 1.152 statute miles.
Times and dates must be valid and follow the format
specified. Dates cannot precede 1980 since DOS will not
recognize any date before 1-Jan-1980. Since the Local Time
display also computes the day-of-the-week, this feature will
allow the determination of the day-of-the-week on which some
future date will occur, such as a birthday or Christmas.
The displayed map can be centered on the US, on Europe, or on
the Far East with this option. There is no effect on the
12/24 HOUR SELECTION
The times displayed with the cities on the map can be
presented in either US 12/Hr format or Intl 24/Hr format
using this option.
Any city in the GeoChron city list can be designated the
Local time city. The Local Time strip in the black area
below the map will take on the attributes of this designated
city and the LocalZone marker on the top scale will move.
When a new LocalZone is selected the times in all cities
remain unchanged. Only the alarm, local time strip and other
features using the local time are affected.
A Help Screen with a Brief description of these features is
available in a window within the [Settings] option of the
When you have chosen a configuration of features and cities
that you prefer, they can be saved to the GC.DAT file and
subsequently automatically loaded with the program. Any
changes made in program features or options will be in effect
only for the remainder of the current session unless they are
saved with the [File] command. Once a new configuration is
saved (in file GC.DAT) the previous configuration is lost.
Be sure you have saved a backup copy of the original program
and data files in case you want to start over or reinstate
the original options. A file called GCDAT.BAK is provided
as a backup duplicate of the GC.DAT file. Ensure that
the file containing the information you want displayed is
The [Cities] settings command allows the user to see and
change the attributes of the cities provided in the GeoChron
database. For example, any city can be excluded or included
from the map display. The following information about each
city is displayed and can be altered as indicated.
CODE - The city code is a three letter designation in capital
letters. Any code except LOC and XXX can be selected. This
code is used to identify the city on the map and to select
and save city features.
INCLUDE/EXCLUDE - If this parameter is set to INCL, the city
is included in the map display; if EXCL is selected, the city
will not be displayed. The [List] command will provide a
list of all of the cities in the GeoChron database,
indicating whether or not they are included in the display.
Although the default settings do NOT include all of the
cities, all cities are designed to fit on the display map
without overlap (although leaving a somewhat cluttered
ZONE - The zone parameter represents the number of timezones
east (positive) or west (negative) of the Prime Meridian
(Greenwich, England) that the subject city lies. For example
New York Zone is -5.0 and Paris is 1.0. Some cities are in
timezones which are not an exact integer number of hours from
GMT (Greenwich Mean Time). Bombay, India, for example, is 5
and one-half hours ahead of GMT. Its zone is indicated as
5.30, with the 30 indicating 30 minutes more advance than
five hours. The zone parameter is for information purposes
and cannot ordinarily be changed.
This parameter is either 1 (if Daylight Savings Time is ever
applicable to this city) or 0 (if is not).
This is a four digit value which indicates the month and day
that is the first day of daylight savings time. It is
specified in the form MMDD, so 0531 would mean May 31st is
the first day of daylight savings time. DD can be specified
as 00 to indicate that the day should be the last Sunday of
that particular month; for example 0400 would mean that
daylight savings time should start the last Sunday of April.
This value indicates the LAST day of daylight savings time.
Otherwise, the comments indicated above for START apply.
Note that it is possible for the END date to precede the
START date when summer comes in the months of December,
January and February as it does in the Southern hemisphere.