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 . (p. 81)