I have to say it is a nice operating system to use. It has its quirks though. We had issues getting it to run on somewhat recent hardware - it wouldn't even complete its bootup. That said, if you are able to get it to run on your hardware, it is rock-solid. Driver development for it was a breeze. I had gone from never writing a driver for it to having a usable one in a day or so. The driver was mature enough after about 2 weeks that I haven't had to touch it since in 6 years. I haven't used the development tools for their UI much so I can't speak to their usability.

I don't know for sure, but in general, ephemeris calculations rely heavily on time. Now they probably convert everything to a common reference frame, J2000 for example based on January 1, 2000, but I'm not sure. I know we typically worry when our stuff rolls over on the new year due to similar issues. The difference is my stuff doesn't end up flinging astronauts into the ground if its wrong. For those who don't know what it means, ephemeris is used to determine position in space. IANARS (Rocket Scientist), but I work for a bunch of them.