I have published ICS calendar, which users filles with own meetings on web frontend.
Currently I got problem, that iOS devices iPhones and iPads are not showing updates, since it stuck to last compatible version.
After digging I found that one user entered EURO € sign to meeting description, and since then all iOS devices stoped updating this ICS.
On Macbooks calendar this is showen without problems. ICS encoding is default UTF-8.
It turned out that EURO € sign is fully supported in iOS, at least tested on version 8.4 and 9.
The problem was non standard all day event description, not the Euro sign it self.