[Bug-gcal] gcal (gnucalendar): BUG: MOONRISE/SET CALCULATIONS: TIMEZONE -1:00 AT LEAST.

[John McGowan]

There are some bugs in the astronomical calculations. I happened to run
across these (moonrise, moonset but did not check sunrise, sunset or other
calculations) which affect (at least) TimeZone=-01:xx (just off the west
coast of England? I don't live there.)

I finally managed to see what moonrise, sunrise, etc. gcal reports as for
moonrise, sunrise, etc. - namely the one occurring during the local day as
specified by the use of the local adjustments in the astronomical special
text sections (NOT the time-offset), such as:
   %(+{latitude_longitude},{adjustment}
where the [adjustment] is (+|-)[hh:mm|mmm].

For some reason, in trying to check what gcal really does I was calculating
moon rise in NYC (of course the moon rises more than once during the course
of the year) and seeing which of those moon rises was reported as an event
occurring on 10th May 2010 in various time zones. There is a problem with
at least one time zone.

MOON RISE:

COMMAND:
   gcal -f/dev/null -# "0 B %(+403600-0741012,[local_adjustment]" %20100510
(May tenth 2010 - find the universal times for moonrises in NYC and see which
of those universal times are reported as occuring for different time zones,
i.e. which moonrise time it chooses to report if it was reporting a moonrise)

                                                                 RESULTS
  gcal -f/dev/null -# "0 B %(+403600-0741012,-3:00" %20100510     4:33
  gcal -f/dev/null -# "0 B %(+403600-0741012,-2:00" %20100510     5:33
  gcal -f/dev/null -# "0 B %(+403600-0741012,-1:00" %20100510     7:33
  gcal -f/dev/null -# "0 B %(+403600-0741012,0:00" %20100510      7:33
  gcal -f/dev/null -# "0 B %(+403600-0741012,1:00" %20100510      8:33
  gcal -f/dev/null -# "0 B %(+403600-0741012,2:00" %20100510      9:33

  gcal -f/dev/null -# "0 B %(+403600-0741012,-1:30" %20100510     7:03
  gcal -f/dev/null -# "0 B %(+403600-0741012,-0:30" %20100510     7:03

As these use the local ajustment to report the local time, the UT of the 
moonrise
selected is obtained by sutracting the local adjustment from the reported local
times giving:

    TZ     Calculated moonrise UT
  -3:00    7:33
  -2:00    7:33
  -1:30    8:33
  -1:00    8:33
  -0:30    7:33
   1:00    7:33
   2:00    7:33

(all these timezones calculate *this* moonrise which occurs during their local
day while other timezone results show that the moonrise for which the 
calculation's
result is presented is the moonrise which occurs during that timezone's local 
day,
such as the one after this, the next day at 07:58 UT which is used in TZ=-8)

and it appears that the moonrise using TZ=-1:xx is calculated as occuring
at 8:33 UT while using the other time zones shows it occurring at 7:33 UT.


The same occurs for:

MOON SET:

COMMAND:
   gcal -f/dev/null -# "0 B %)+403600-0741012,[local_adjustment]" %20100510

  gcal -f/dev/null -# "0 B %)+403600-0741012,-3:00" %20100510     17:51
  gcal -f/dev/null -# "0 B %)+403600-0741012,-2:00" %20100510     18:51
  gcal -f/dev/null -# "0 B %)+403600-0741012,-1:00" %20100510     20:51
  gcal -f/dev/null -# "0 B %)+403600-0741012,0:00" %20100510      20:51
  gcal -f/dev/null -# "0 B %)+403600-0741012,1:00" %20100510      21:51
  gcal -f/dev/null -# "0 B %)+403600-0741012,2:00" %20100510      22:51

  gcal -f/dev/null -# "0 B %)+403600-0741012,-1:30" %20100510     20:21
  gcal -f/dev/null -# "0 B %)+403600-0741012,-0:30" %20100510     20:21

As these use the local ajustment to report the local time, the UT of the 
moonrise
selected is obtained by sutracting the local adjustment from the reported local
times giving (as the calculated moonset in NYC reported as occuring during the
local day, 10th May 2010 in various timezones):
:

    TZ     Calculated moonrise UT (time reported minus TZ)
  -3:00    20:51
  -2:00    20:51
  -1:30    21:51
  -1:00    21:51
  -0:30    20:51
   1:00    20:51
   2:00    20:51

and it appears that the moonrise using TZ=-1:xx is calculated as occuring
at 8:33 UT while using the other time zones shows it occurring at 7:33.