World by Day and Night
by Glynn Clements

Running this application opens a window on the Desktop showing an outline
map of the world, over which is superimposed the sun in its current
position, and a band of yellow shading. The area of yellow represents
daylight, while the unshaded area represents night. The title bar of the
window shows the current time (GMT by default).

Clicking Menu over the window offers a number of options. Info leads
to a standard information box. Display allows you to alter the position of
the map in the horizontal (i.e. latitudinal) plane relative to either earth
or sun position.

Scale allows you to alter the scale of the display. The window size will
change accordingly.

The Time/date option leads to a submenu offering a choice between instant
time or real time, plus an option to add an offset to GMT to allow the
displayed time to reflect any time zone. Instant time leads to a dialogue
box into which the desired date and time can be entered. The display will
then show the position of the sun at that time. Real time on the other hand
provides a continuously updated display based on the current time. Because
the information in the window is complex, redraw speed is quite slow, so the
window is only updated once a minute. The Offset option enables you to
specify an offset from GMT, which will then become the default when you next
run the program.

Grid allows you to place grid lines on the display. You can choose a grid
based on the earth position, sun position or latitude. Additionally you can
display the tropics and poles. Any or all these grids can be overlaid at the
same time.

Two further options, Sun and Shading, allow you to choose whether to display
the position of the sun, and whether to turn the shading on or off. If the
shading is off, a line is drawn to indicate the division between day and
night.

Finally, the Quit option quits the application and removes the window from
the screen.

