Years were counted from the beginning of each new emperor. A year was made up of twelve lunar months. An extra month was added seven times every nineteen years. An intercalary month was added during the summer when a month would begin and end in the same zodiac sign.
The new year began with the first new moon after the sun had entered Aquarius. The months were named by number, e.g., first month, second month. Years were named in groups of twelve: Rat, Ox, Tiger, Hare (Rabbit), Dragon, Snake, Horse, Sheep (Goat), Monkey, Rooster, Dog, and Pig. The list was repeated after it had been completed.