Extended Timeline uses a different map than the base game does. The map of Extended Timeline is based on Typus Orbis Terrarum by Bizarcasm. Extended Timeline further modifies the map by adding many new provinces and moving the borders to better accommodate both the ancient and the modern world.
Below is a map with the IDs of every land province in the mod. The map is up to date as of Extended Timeline version 1.11.1. The province IDs can also be seen by using the console command debug_mode in the game and hovering over the provinces.