A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Iwancio
Date: 2019 Jul 10, 17:55 -0700
I have doubts about that stated precision that far into the future, at least for longitude. We can't predict leap seconds in UTC that far in advance.
Right now, the latest version of USNO's MICA application (last updated 2012 January) is about 1 second behind UT1, so it'd put you around 0.25' west of your true longitude. Predictions published in 2000 in HMNAO's "Planetary and Lunar Coordinates 2001-2020" would put you about 4.2' west today. I have no idea what the prediction models looked like back in 1978.
If you keep track of the difference between how many leap seconds we've had and how many Tamaya's software developers thought we'd have, you could determine the difference between actual UT1 and "Tamaya Zone Time" to compensate. Or you can just decide whether that much error is worth worrying about.