Topsy-Turvy is an equinoctial festival celebrated primarily in sub-Hazari lands, including among many Bissenke populations. Just as the days and nights are about to "flip" from longer days to longer nights, this is a time when ordinary social conventions are likewise turned over on their heads for the day. The roles and dress of women and men may be reversed, servants may give orders to chieftans, children can boss around adults, slaves and servants may dress in mockery of their supposed betters, and many other small reversals play out through the course of the day. It's also a day for pranks and jokes -- usually though not always light-hearted, sometimes disruptive.
Given Omrazir's cosmopolitan nature and its many ties to broader Idiri culture, Topsy-Turvy is celebrated by many there too (hence its appearance on the main calendar). Other places in the western caliphate can also be found observing the chaotic customs of the day, typically in places where Bissenke or other sub-Hazari influences are pronounced. It's generally not a thing in the eastern caliphate, though even there you might find some small communities celebrating it among themselves.
As for other holidays, yes, there are a number of others that should pop up following Topsy-Turvy! The Kingfisher Festival will be the next one, which celebrates the seasonal return of Omrazir's beloved kingfishers to the city. Some coastal cities in Marzum and various other provinces often have their own versions of this, though Omrazir's is one of the largest and most riotous -- non-festival business virtually shuts down for a few days, people dress up in bright colors and costumes, there's music and dancing and games, and a generally carnival-like atmosphere prevails. Kingfishers are associated with the prophet al-Azad, which is part of why they're so loved, but people also just enjoy having such colorful characters as the kingfishers around for the winter months.
Kholabi brings the Day of All Souls Dreaming, as mentioned in the Remembering the Dead thread right before this one, and the days of restless spirits following it.
After that, in Oniris, is the Day of Remembrance, a solemn observation of the anniversary of the eruption of Mt. Elemnis and the start of the Great Dark.
Darshali brings the Festival of the Dead (a much more light-hearted remembrance and honoring of the departed than in Kholabi) and the Fire Festival (this latter originally an Irzali/Elestaarian holiday period, but now spread across the caliphate as a secular festival).
There are other feasts and festivals besides these, but I think these are the most prominent ones coming up before (our) year's end. Like SO MANY THINGS, holidays need to be better documented and in some cases tweaked a little, but hopefully this answers a few small immediate questions. But if you have others please ask!
