As jerf pointed out [0], you can do that but once you print that unknown symbol, the Unicode consortium can't really do much.
Also, you can't just say "well, next era begins on September 1st 2054, so let's write that in our date calculator" - precisely because you don't know when an era begins or ends before it's close.
Also, you can't just say "well, next era begins on September 1st 2054, so let's write that in our date calculator" - precisely because you don't know when an era begins or ends before it's close.
[0] https://news.ycombinator.com/item?id=17609063