A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2021 Jan 6, 23:38 -0800
That is strange. I opened my almanac and set it to 2021, Jan 1 at 00:00:00 UT1 and the result I got was 179°08.5' ... which agrees with the other sources you checked. (See attached screenshot.) I don't know why it would behave differently for you. Even unchecking the TAI-UT1 box made no difference. (Well, it changed the altitude by a tenth of a minute, but that is negligible.) The only reason I can think of is maybe if the spreadsheet is opened in a different version of Excel - or a different spreadsheet program altogether - it may not work correctly. I don't know, but I doubt that you are doing anything wrong.
But this is exactly the kind of thing I was hoping to find out: if it works on other people's machines.So thank you for testing it and reporting the problem. I will investigate and see if I can find the cause.