For life on other planets, I wonder how they would treat a solstice on their planet? To be high level sentient does one have to be a pattern seeker, to look for the meaning and/or reasons for the patterns? If so, then such sentient beings would see the pattern of solstice and equinox as even our distant ancestors did (from even before Stonehenge) and work to apply a meaning or reason to the pattern (for to find meaning or reason is to find purpose and to be able to make predictions, and maybe even gain some control over - or at least the illusion/delusion of some control).However, I am making an assumption - that while for humans have shown a great interest in marking solstices and equinoxes from prehistoric times, an alien mind, on the other-hand, may not place any special or theological meaning to such cyclical patterns as a solstice or an equinox. Solstice may not mean squat to them, and they would be confused by our making such a big deal out of it. For them, if they have religion, their religious mind set may have them find other patterns to be special and worthy of note. Maybe they place the birth of their god in the middle of Spring, between a solstice or an equinox. Maybe their sun isn't important to them (a blind species, or a species that lives under the ice - getting their energy from thermal vents and not the sun, or a subterranean species...). Maybe they have two or three suns and the special days are more complicated and arrive less often.
This, of course, depends on many factors which would affect the severity, or the placidity, of annual weather patterns. Is the planet in a very circular orbit, or a somewhat elliptical one? Is the planet close to its star, and thus with a very short year? Is the planet actually a large habitable moon circling a gas giant? Is there a virtually non-existent tilt to its axis or it is a large tilt? And what of these combined?
Another question is if there is one God, surely He would be interested in all of His spiritual children ("other children have I"....?), and if so, would He then visit other planets? How would He visit them? Would we recognize that He did in their religious texts and stories?
I leave you to ponder such questions during this holiday season - though for us, what is important is our own here and now: have a happy and safe holiday season.