org-table change time from UTC to other timezones

["Alan E. Davis" <lngndvs@gmail.com>]

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I have been pleased to learn that I can add / subtract hours in org-table
to shift time zones.  I am making tables of  lunar/solar parameters
relevant to tides.  Org-table is a convenient way to enter data in a
tabular format that can be printed via LaTeX.  So each year, for several
time zones, I enter these times by hand.

It's very, very easy, I have learned, to collect all of these times (at
most, maybe 12 per month) for UTC, and add or subtract to generate a column
of times for a new time zone.  Very Slick!

Except that when I add, for example. 09:00 to 23:33, I guess it is pretty
obvious what is going to happen: it would be the same day, but at 32:33 !!

I have tripped up on trying to test for whether the sum is greater than or
equal to 24:00, and then doing something interesting with it.  It's
actually pretty easy to go through all the months and find the exceptions,
and make manual changes.  But, as I usually have done, I would rather spend
a few hours coming up with some programmatic method for making this work
automatically!

The other problem is the change of the day.  I suppose I could use 0, 1,
2... for Sunday, Monday, Tuesday...  (I am living in the United States).

Has someone solved this problem?

Thank you,

Alan Davis

-- 
      "This ignorance about the limits of the earth's ability to absorb
       pollutants should be reason enough for caution in the release
       of polluting substances."
                   ---Meadows et al.   1972.  Limits to Growth
<https://www.dartmouth.edu/~library/digital/publishing/meadows/ltg/>.
(p. 81)

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