Time should be a variable that the player can adjust. Standard turns are set a 1 year. If you are developing your culture, the turns should be variable between 1, 10, and 100 years, max. If you are attacked, or engage in war, the turns switch to 3 months, fixed until peace is achieved. If you are engaged in diplomacy and trade the activity is registered at the one year level. Your leaders grow old and die and you have heirs.