Why is Tiger the number three of Zodiac Sign?

Ancient Chinese people figured out a way to record the chronological sequence of events. Heavenly stems and earthly branches are established. The earthly branches include 子 丑 寅 卯 辰 巳 午 未 申 酉 戌 亥 (zǐ chǒu yín maǒ chén sì wǔ weì shēn yǒu xū haì). And they divided a day into 12 hours and found 12 representative animals to mark each hour. How did they put these animals in order? They made an order based on their activity. Rat is active from 23:00 to 01:00. So it ranks as No.1. Ox is active from 01:00 to 03:00 so that it ranks as no.2. Tiger is active from 03:00 to 05:00. So it ranks as no.3.