I don't know if you can change what a location's era in the save screen by modifying memory.
It's stored in a table in the ROM.
3FD296 3FD395 DATA N Location Age Name string used (half byte per location) 2007.02.09
Ack! I overlooked that in the memory pointers.txt that Gieger provided. Well, I'll give it a shot. What I'm trying to do is make it so that when the Player saves on a brand new map I created, it will say the "???" instead of saying "Middle Ages"
If it's not editable, it could become a good feature suggestion for a future edition of TemporalFlux, especially seeing as alot of people are going to want to be able to change this.