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a "year" that didn't quite match the earth's actual motion around
the sun,  and by 1582,  a ten-day error had accumulated.

   So in 1582,  Pope Gregory declared that a new calendar would
be put into effect:  October 4 would be followed by October 15,
and certain leap days would be omitted in the future.  If you
look at October 1582 in the Time Dialog,  you should see this
odd state of affairs,  with ten days "missing".

   Most of the time,  when you see a pre-1582 date such as
10 Nov 1444,  that date will be in the Julian calendar,  and a
date such as 20 Jan 1812 will be in the Gregorian calendar.
By default,  Guide uses this "Gregorian/Julian" system.  But
exceptions occur.  Some countries (notably Protestant ones)
didn't switch over until much later:  Britain and its colonies
in 1752,  Russia/the USSR in 1918.  So the Time Format dialog
offers "Julian" and "Gregorian" options,  to force the use of
one particular flavor of the calendar.

   Dates can also be shown in several other calendars,  such as
the Jewish,  Islamic,  and French (Republican) calendars.  It's not
likely that you will wish to do that.  But at the end of "Quick
Info" (see page 15),  Guide does give the current date as expressed
in each of these calendars.  And if,  for some reason, you do
wish to have all dates shown using,  say,  the Persian calendar,
you can do so.

   Clicking on "Current Time"  causes Guide to look at your computer's
clock and to use its date and time.  You can get the same effect at
any point in the program by hitting the F3 key,  or by clicking with
the right mouse button on the time shown in the legend area.

   Clicking on any of the twelve month keys resets the time to the same
date in that month.

   Outside the Time dialog,  hit Alt-0 to reset the time to midnight UT.

   If you want to reset the date/time by typing in something like
"2008 Jan 17" or "11 Dec 4:42" or "13:26",  use the "Enter Time"
feature in the Settings menu (page 30),  or left-click on the
time zone shown in the legend.

15:  PLANETARY ANIMATION AND EPHEMERIS CREATION       

   Using the Animation Menu you can watch planets, asteroids,
satellites, comets and stars move in time-lapse animation. This menu
may also be used to record the tracks left by an object over time or
to list ephemerides in a file.  For reasons that will become apparent,
animation,  ephemerides, and tracks are linked concepts in Guide.

   From the main menu,  use the Animation option. The Animation Menu
looks like this:

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