Yes, the Sun is pretty darn far away too (93 million miles on average). Let's say the date and time used as an input to their astrology algorithm is off by 12 hours, since this would place them on the other side of the Earth for a given day (7917.5 miles away). This represents only a 0.0085% and 0.0020% error in the distance to the Sun and Jupiter, respectively.
What I'm saying is that calling out errors in DST and time zone is not a very scientific debunk of your friend's interest. I'm not a practitioner of astrology myself. However, I like to keep an open mind on nearly any topic, especially on something as harmless as astrology. I hope your friend didn't take the criticism too hard. It's always a bummer to find an interest or hobby that brings you joy, just to have it torn down by someone who you respect.
Also, just this week I saw an article posted on Lemmy about how studies show a full moon negatively impacts sleep quality, even if you are in a room with no windows and can't be influenced by the additional light. There's clearly still things about gravitational bodies we don't yet understand.