It seems that the site calendar (upcoming events) does not include holidays such as Yom Haatzmaut and Yom Yerushalaim. Would it be possible to add them, so users can easily see posts about them at times like this?
I've been doing the Community Events lately. There are various special days I don't tend to do them for, such as Rosh Chodesh, T"U Bishevat, and minor fasts. I don't choose what to put up based on a formal rule (so far), but it's basically parashat hashavua' and major holidays that we have lots of material on.
Yom Ha'atzma'ut is a major holiday for many Jews, it's not a holiday at all for many Jews, and it's a minor observance for many Jews. Our tag for it, yom-haatzmaut, has only 19 questions so far. So, I'm not sure whether it's worthwhile to put up a Community Event for it or not. Yom Yerushalayim is a major holiday for fewer Jews than Yom Ha'atzma'ut is, and our tag for it, yom-yerushalayom-yerushalayim, has only 9 questions so far.
To make this into a votable answer: status quo is that I don't bother with Y"H or Y"Y until such time as their tags become richer sources of material.
Alternative answers are welcome. I'll be happy to follow the will of the community.