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   Right at the top is Guide's idea of what the time is. By clicking
on a button above a figure,  you can increment it;  for example,
each time you click above the '9' in 1985, you will go forward by a
century.  By clicking on a button below a digit,  you can decrement
it. If you only want to change a few figures a small amount and don't
want to reach for the keyboard,  this can be very convenient.

   After clicking on the year,  hour,  minute and second fields on
the second line you may enter those values from the keyboard. This
would, for example, be the fastest way to go from 1985 to -333.

   When you enter an hour,  you can also reset the minutes by entering
something like "3:14";  or you can reset the hours, minutes and
seconds with something like "3:14:16".

   Historians and astronomers differ on years before 1 AD. Historians
do not use a year zero. To them,  the year before 1 AD is 1 BC.
Astronomers say that the year before 1 AD is 0,  and the year before
that, -1.  This causes a one-year difference:  if astronomers say an
eclipse occurred on 28 Aug -1203,  historians say it happened on 28
Aug 1204 BC.  Guide sides with the astronomers, recognizes the year
0,  and expects -1203 to be entered in the above instance.

   You can click on the days shown in the calendar for the current
month, plus the usual partial calendars for the previous and
following months, shown in the next six lines. This is a fast way to
back up or move ahead a few weeks.
                                                           
   The "Time Zone  UT" option lets you tell Guide what time zone you
are using.  By default,  Guide displays all times in UT (Universal Time,
basically Greenwich Time),  but clicking on this option brings up a long
list of the world's time zones.  You can also select "time zones" such
as local sidereal time,  local mean time,  Dynamical Time,  etc.  These
are not really "time zones",  but selecting them means that Guide will
display all times in those systems and will expect times you enter to
be in those systems.

  The zone you select need not match the one used by your computer's
clock.  If you wish to have Guide show times in UT,  even though
your PC clock is set to a local time zone, this is not a problem.
                                                              
  The "JD..." option lets you both see and reset the Julian Day.
The Julian Day system (no relation to the Julian calendar) is in
common use by astronomers;  it specifies time in terms of days
since noon, 1 Jan 4712 BC.  Thus,  1 Jan 2000 is JD 2451545.; that
is how many days will have elapsed since 1 Jan 4712 BC.  As you
alter the time,  the value shown here will change,  and if you
click on it, you will be asked to specify the time by Julian Day.      

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