How not to land on Venus

I'd actually thought we'd figured out the length of Venus' day already but - apparently not. UCLA say it depends.

Venus' atmosphere, running against the cliffs of the various Regiones and Terrae, pushes the land one way and then the other. It's like ocean tides over here. Solar tides, to be sure, but then Venus is closer to our Sun.

The Venus day is, therefore, an average: 243.0226 of our days. The actual day might run twenty minutes more or less than that. By the way this also means if you want to land at, say, Aphrodite Terra you could find your target off by 30 km. I think Maxwell Montes, near-polar as it is, might be better.

Also narrowed down is inclination, which changes like ours, but at least at a predictable rate. It's 2.6392 degrees now (I think you'd subtract 180 from that but, hey); it precesses at 29 kyear, comparable to our 26.

And there's a core: 3500 km "across" but UCLA must mean radius because they further liken that to Earth's [3485 km radius] core. They don't know if the core is liquid. It might not even matter if the core's movement is stalled; hence the lack of magnetic-field here.