Era (Civ4)

An era is a period of time in Civilization IV and its expansions. Civilizations can progress to a new era by researching new technologies.
The eras in the game are:
* The Ancient Era is the first time period of the game (4000 BC Start).
* The Classical Era is the second time period of the game (2000 BC Start).
* The Medieval Era is the third time period of the game (250 AD Start).
* The Renaissance Era is the fourth time period of the game (1250 AD Start).
* The Industrial Era is the fifth time period of the game (1700 AD Start).
* The Modern Era is the sixth time period of the game (1905 AD Start).
* The Future Era is the seventh and final time period of the game (1980 AD Start).
== Effect of Eras ==
=== Gameplay Changes ===
* AIs are less willing to sell techs to Civilizations with more advanced Era.
=== Cosmetic Changes ===
* Cities change their appearance in Medieval, Renaissance, Industrial, and Modern Eras.
* Workers change to their modern look in the Industrial Era.
* Most Improvements change their appearance in the Industrial Era.
* Windmills change their appearance to one resembling wind turbines in Modern Era.
* The background music, as well as diplomacy screen music, changes with the player's current Era.
* The sound used when winning or losing a battle changes in Medieval and Modern Eras.
== Trivia ==
* Internally, units change appearance based on Early, Middle, and Late era group tags. Ancient and Classical Eras belong to Early, Medieval and Renaissance Eras belong to Middle, and Industrial, Modern and Future belong to Late era group. According to the DLL code:
** Early: The first quarter (rounded up) of the Eras.
** Middle: Eras not belonging to Early or Late group.
** Late: The last half (rounded down) of the Eras.
== See also ==
* Era in other games